I bought the expansion a few minutes after it was available to purchase on Steam. The Dev team has put a ton of work in making Civ V better and even if the expansion ends up being less than ideal I trust them to make it right.
You had a pretty bad experience with the vanilla game so my advice to you Davor would be to wait it out and see what the fanbase says. Avoid the review sites at all cost because if you recall they were throwing 90% around when the game first came out which was a total crock. I wouldn't give Civ V a 90% now nevermind 18 months ago. The only site that gave an honest review in my opinion was 1UP which threw the game a C- which may have been a little low but certainly much more representative of the true quality.
Anyway, welcome back.