Sure.
My group and I had started a 3.0 campaign and included a few houserules, when 3.5 came out. We looked at it in detail, even buying the books, but as the game had been working out perfectly, and noone abused the loopholes, we stayed our course. We do use the new monsters from the other monster manuals, however, as well as the updates to the MM I (outsiders and some others). I use 3.5 for online and play-by-post gaming, however, and I still feel the difference is really not big enough to justify all the fierce discussions.
So, not wanting to start a 3.x discussion here, but to explain a bit: Most of my group felt that 3.5 came too early, and, although it closed some issues with rules, it also failed to address many others, while at the same time opening new ones (including some pretty significant issues).
Personally, I felt that although I guess 3.5 was a commercial success for WotC, it broke the concensus in the gaming community -- with 3.0, in spite of the usual discussions and houserulings, there was only one official rules canon to refer to. With 3.5 that changed, and suddenly there were two reference points (because people had to compare, and some did not make the step to 3.5, or decided to only partially adopt new rules). I think in this regard, the birth of Pathfinder (pretty neat in picking up the 3.x legacy) really has its roots in the step from 3.0 to 3.5.