Do you play the official or the SVN?
SVN.
1) Alot of people already mentioned the overwhelming superiority of the Despotism over any other early civic but I found myself using it untill industrial era . How long do you guyz stick to Despotism ?
Many times until I get Democracy.
2) I couldn't find any practical use for Crossbowman, I find idea of having any in the stack rather useles. Does someone actualy knows how to use them effective enough ?
They will crush those that are still using mainly swordman type units. A combination of Longbowman and pikeman will be better for defense eventually, but they're not bad to beat back those bronze and iron working units and they're cheap enough as well.
3) Also I can't find any reason to build Levies/Irregulars at all. Their cost is almost as theirs proffesional counterparts and food production doesn't cover the strenght difference at all. Does anyone actualy use them ?
Some cities have enough food but not hammers, so yeah. And cities with hammers and food can build them quite fast. Thats pretty much it. They are cheaper for sure, so they serve as good cannon fodder when trying to not waste too much production, for example when trying to conquer cities with tribal forts (heh)...
4) Again about the Great Library(I think this wonder is way overpowered). In every game I played I was able to build it even without marble, AI simply ignore this tech for some reason. Is it just my luck ?
Its not that hard to beat the AI to important wonders, especially since you can almost always get the pyramids and the great engineer that will pop, saving it for something important. The AI doesn't really wonder whore unless its isolated (sometimes the English on the huge world map will wonder whore like crazy). In my current game with the Zulu on the the huge world map/Immortal I built 8 world wonders without trying (not pyramids though, I just started by craking out settlers and workers) and still in Medieval era with 14 cities (two more on the way, since the remaining Swahili cities lost their tribal forts).
If you think the great library is great put it together with Gondeshapur and see yourself getting the tech lead vs Immortal AIs. I had to close some borders so that they don't catch up easily!
Btw I hate that cities take so long to culture flip even when they have just the one city tile, made me lose my patience and waste like 15 units.
5) I played 2 games with tech transfer and found it enjoyable early on but not quiet what I like later on, I had to feed the AI techs through the map editor in order to keep them on pair. It is more of a personal preference but I like it when even small civilizations(or big but that fell behind in sciense too much) can posses threat strong enough to send troops on them. How do you guyz play it ? With techtransfer or in old way ?
With tech transfer. What difficulty are we talking about? Just step it up.