Things to keep in mind on Emperor
1. The AI's start with POTTERY and ANIMAL HUSBANDRY (not just POTTERY).
2. Your BARB bonus drops from 25% to 10% (AI's stay at 60%), so Barbas are more dangerous. Also the range at which BARBS can start hunting you increases.
3. AI gets a free WORKER and SCOUT and an extra WARRIOR. (So get a scout very early if you want a shot at any RUINS bonus)
4. The AI's happiness gets scaled at 70% rather then 90% on king, so happiness is less of a concern for them especially as the game progress.
5. The AI's ability to produce things gets a buff (be it training unit, buildings etc). I don't understand the bit about GROWTH % though, have to delve into the base code to work that one out.
6. Purchase and supply for units gets a buff. AI's with gold are particularly dangerous as the difficulty increases.
That's mostly it, have a look at the XML I have linked for more info. Remember an AI with more resources often behaves "smarter" then one without, not because the code has changed but because they have access to more options.
THINGS TO CONSIDER
1. Expect war earlier (as the AI has more resources to do it). Obviously more MILITANT or WARMONGER Civs are more prone to this then peaceful ones.
2. Keep your military strength higher (check demographics for where you stand on this), it will tend to give you better diplomatic relations and help insulate you from DOWS and DENOUNCEMENTS (all other things being equal of course).
3. The AI will get more Wonders so put more effort into the ones you want.
Probably a whole lot more but others can fill you in further.
In the end how difficult you find it will depend on how much your current gameplay is reliant of specific mechanics. Wonder whoring gets harder, CS become harder to get etc etc.
If your win times are based on a balanced gameplay style (and not the result of incessant reloading) then I think you will find EMPEROR more then winnable, especially after your first game. BTW : I am not criticising reloading here, just pointing out that if you do it to get out of trouble you will find higher difficulties harder then if you learn to cope with and recover from the situation.
Here is the XML if you are interested, its pretty easy to interpret, for the most part.
LINKED FROM : C:\Program Files (x86)\Steam\steamapps\common\Sid Meier's Civilization V\assets\Gameplay\XML\GameInfo\CIV5HandicapInfos.xml
Code:
-<Row><Type>HANDICAP_KING</Type><Description>TXT_KEY_HANDICAP_KING</Description><Help>TXT_KEY_HANDICAP_KING_HELP</Help><StartingLocPercent>50</StartingLocPercent><AdvancedStartPointsMod>90</AdvancedStartPointsMod><HappinessDefault>9</HappinessDefault><NumCitiesUnhappinessMod>100</NumCitiesUnhappinessMod><PopulationUnhappinessMod>100</PopulationUnhappinessMod><Gold>0</Gold><GoldFreeUnits>0</GoldFreeUnits><ProductionFreeUnits>5</ProductionFreeUnits><ProductionFreeUnitsPopulationPercent>50</ProductionFreeUnitsPopulationPercent><ProductionFreeUnitsPerCity>2</ProductionFreeUnitsPerCity><RouteCostPercent>100</RouteCostPercent><UnitCostPercent>100</UnitCostPercent><BuildingCostPercent>100</BuildingCostPercent><ResearchPercent>100</ResearchPercent><PolicyPercent>100</PolicyPercent><ImprovementCostPercent>100</ImprovementCostPercent><CityProductionNumOptionsConsidered>2</CityProductionNumOptionsConsidered><TechNumOptionsConsidered>2</TechNumOptionsConsidered><PolicyNumOptionsConsidered>2</PolicyNumOptionsConsidered>
<!--<InflationPercent>100</InflationPercent>-->
<AttitudeChange>-1</AttitudeChange><NoTechTradeModifier>50</NoTechTradeModifier><BarbCampGold>25</BarbCampGold><BarbSpawnMod>0</BarbSpawnMod><BarbarianBonus>25</BarbarianBonus><AIBarbarianBonus>60</AIBarbarianBonus><EarliestBarbarianReleaseTurn>0</EarliestBarbarianReleaseTurn><BarbarianLandTargetRange>5</BarbarianLandTargetRange><BarbarianSeaTargetRange>12</BarbarianSeaTargetRange><AIStartingDefenseUnits>1</AIStartingDefenseUnits><AIDeclareWarProb>100</AIDeclareWarProb><AIWorkRateModifier>20</AIWorkRateModifier><AIUnhappinessPercent>90</AIUnhappinessPercent><AIGrowthPercent>90</AIGrowthPercent><AITrainPercent>85</AITrainPercent><AIWorldTrainPercent>100</AIWorldTrainPercent><AIConstructPercent>85</AIConstructPercent><AIWorldConstructPercent>100</AIWorldConstructPercent><AICreatePercent>85</AICreatePercent><AIWorldCreatePercent>100</AIWorldCreatePercent><AIBuildingCostPercent>85</AIBuildingCostPercent><AIUnitCostPercent>80</AIUnitCostPercent><AIUnitSupplyPercent>30</AIUnitSupplyPercent><AIUnitUpgradePercent>50</AIUnitUpgradePercent>
<!--<AIInflationPercent>80</AIInflationPercent>-->
<AIPerEraModifier>-2</AIPerEraModifier><AIAdvancedStartPercent>120</AIAdvancedStartPercent><IconAtlas>DIFFICULTY_ATLAS</IconAtlas><PortraitIndex>4</PortraitIndex></Row>-<Row><Type>HANDICAP_EMPEROR</Type><Description>TXT_KEY_HANDICAP_EMPEROR</Description><Help>TXT_KEY_HANDICAP_EMPEROR_HELP</Help><StartingLocPercent>50</StartingLocPercent><AdvancedStartPointsMod>85</AdvancedStartPointsMod><HappinessDefault>9</HappinessDefault><NumCitiesUnhappinessMod>100</NumCitiesUnhappinessMod><PopulationUnhappinessMod>100</PopulationUnhappinessMod><Gold>0</Gold><GoldFreeUnits>0</GoldFreeUnits><ProductionFreeUnits>5</ProductionFreeUnits><ProductionFreeUnitsPopulationPercent>50</ProductionFreeUnitsPopulationPercent><ProductionFreeUnitsPerCity>2</ProductionFreeUnitsPerCity><RouteCostPercent>100</RouteCostPercent><UnitCostPercent>100</UnitCostPercent><BuildingCostPercent>100</BuildingCostPercent><ResearchPercent>100</ResearchPercent><PolicyPercent>100</PolicyPercent><ImprovementCostPercent>100</ImprovementCostPercent><CityProductionNumOptionsConsidered>2</CityProductionNumOptionsConsidered><TechNumOptionsConsidered>2</TechNumOptionsConsidered><PolicyNumOptionsConsidered>2</PolicyNumOptionsConsidered>
<!--<InflationPercent>100</InflationPercent>-->
<AttitudeChange>-1</AttitudeChange><NoTechTradeModifier>40</NoTechTradeModifier><BarbCampGold>25</BarbCampGold><BarbSpawnMod>0</BarbSpawnMod><BarbarianBonus>20</BarbarianBonus><AIBarbarianBonus>60</AIBarbarianBonus><EarliestBarbarianReleaseTurn>0</EarliestBarbarianReleaseTurn><BarbarianLandTargetRange>6</BarbarianLandTargetRange><BarbarianSeaTargetRange>15</BarbarianSeaTargetRange><AIStartingDefenseUnits>1</AIStartingDefenseUnits><AIStartingExploreUnits>1</AIStartingExploreUnits><AIDeclareWarProb>100</AIDeclareWarProb><AIWorkRateModifier>50</AIWorkRateModifier><AIUnhappinessPercent>85</AIUnhappinessPercent><AIGrowthPercent>85</AIGrowthPercent><AITrainPercent>80</AITrainPercent><AIWorldTrainPercent>100</AIWorldTrainPercent><AIConstructPercent>80</AIConstructPercent><AIWorldConstructPercent>100</AIWorldConstructPercent><AICreatePercent>80</AICreatePercent><AIWorldCreatePercent>100</AIWorldCreatePercent><AIBuildingCostPercent>80</AIBuildingCostPercent><AIUnitCostPercent>75</AIUnitCostPercent><AIUnitSupplyPercent>30</AIUnitSupplyPercent><AIUnitUpgradePercent>50</AIUnitUpgradePercent>
<!--<AIInflationPercent>80</AIInflationPercent>-->
<AIPerEraModifier>-3</AIPerEraModifier><AIAdvancedStartPercent>135</AIAdvancedStartPercent><IconAtlas>DIFFICULTY_ATLAS</IconAtlas><PortraitIndex>5</PortraitIndex></Row>