I recently installed CS3 Bridge but not Photoshop (I still have Photoshop CS2 using CR 3.6).
1) Is there any reason to upgrade to CR 4.1 other than more cameras supported, i.e., any enhancements to CR in 4.1?
You have now started several threads on this same topic. That is not a good idea. I have answered your question in one of your other threads that you started.
However, ACR 4.1 will only work with Photoshop CS3. Adobe says there were too many changes to make it compatible with earlier versions. But it seems to me that it is much a marketing tool to motivate people to move up to the new version as it is a compatibility issue. There is no way to use ACR 4.1 with Photoshop CS2. The latest version you can use is ACR 3.7.