It's a little different. In a sense it's easier because the AI is so bad at combat and unit or city losses have a more substantial effect. Getting beat by one turn for a wonder is a lot more annoying and trying to hold off until you get that one tech you need may take a lot longer than you expect. Slingshots give you a much greater advantage for a much longer time so civs like the Babylonians feel more potent and putting more effort into specialists than your used to doing can greatly improve your game.
You will find use for a lot of units that you basically ignore in faster games. Longswords, Lancers, and Cavalry are all good examples. The industrial and modern ages will take more than a blink of the eye to pass as well. This also makes UUs feel a lot more important, Greece can be a monster in Marathon games because your Hoplites and Companion Cav will be superior for quite some time and you just may actually find a use for B-17s and Zeros.
Production bonuses from social policies also feel a LOT more powerful, the amount of time you can save in new coastal cities is substantial even with +3 hammers.
Anyway, the biggest difference in my opinion is definately combat. Production, gold and research costs are all increased but units have the same 10 hit points so you can cripple a Civ's military for a long time with one good turn of combat.