I was there for a short stay last year for work. Stayed in the JW Marriott, which was a great hotel. The city didn't really seem to have much to offer, I wouldn't want to go as a tourist. And everyone in town knows that the huge building there is the 2nd largest buliding (in terms of sq. footage) in the world, after the Pentagon. I must have heard that like 10 times.
The only redeeming thing about that city for me was the wine shop in the airport. I think I bought 15 bottles of wine for an average of EUR10 -12 each (and somehow managed to fit it all in my carry-on) Romanian and Moldovian wines are absolutely fantastic.
I have been to Bucharest a couple of times. Both times, I was on my way to the Black Sea area, so I only spent a couple of days in Bucharest on the way in and out.
I find it to be an interesting city to tour and learn the history of the Ceaucescu regime and the Revolution. It was interesting for me to go there 14 and 16 years after the Revolution, respectively, and to see how much capitalism had spread in just two years. New businesses, and a greater variety of businesses were all over the place. It was very noticable to me.
Bucharest is pretty clean, and very American-friendly. Not sure what I would do there for an extended period, though.