I've been using CM7 in the past month and was quite satisfied with it.
Last week I've moved to Oxygen and I'm very happy with it.
- It has much-much better battery life than CM7 (see my post
here).
- Oxygen is much smaller, so it fits in 100MB System tables, giving 45MB more space for user apps than CM7. This even allows you to keep the Dalvik cache to
- The ROM is much cleaner, so I don't have to use TB to remove unnecessary things
- Oxygen got recent nice improvements, like theme chooser (like in CM7). This means you have access to 100+ themes for your phone without changing your favorite launcher.
Also, a funny but useful feature is to make a screenshot directly from Power menu. Now you don't need Shootme anymore.
- The ROM seems to be actively developed (now with v2.1.6) and is using the latest Android v2.3.4 with all its improvements.
Bottom line: for me Oxygen is the winner at this moment.