I believe the game is fundamentally sound. It needs some tweaks, but with each patch, so far, the game has improved. I enjoy it quite a bit. I, unlike many others, will not compare it to CiIV BTS. That game was well beyond CiIV Vanilla and Warlords.
The developers designed a damn good game IMO - not perfect, but damn good. Expansion will add elements to gameplay that will make it much more complex and challenging as was done with previous Civilization games. Although many people don't like the game, I enjoy it and will continue to play it through patches and expansions.