I've tried playing it numerous times and struggled around mid to late game, with other civs somehow getting more technology than me. I've never beaten this game once.
It is a very complicated game on many different levels, with religion being one of these levels. However, with enough dedication this game could be beaten, but i've found other games to satisfy my short-term needs at the moment. One day, i'll have another crack at it.
The deepest and best looking game of the Civilization series, but as a result the most complicated. Be wary.