I switched over to Fresh, which helped my battery life a bit.
But, I also noticed an issue with Last.FM. The past few versions have been very buggy and kept my phone from properly sleeping. It'd also *send* a lot of data, and prevented my WiFi from going to sleep. I found that I wouldn't even get a full day out of the phone with light use, and that's with 9 hours in airplane mode and using Fresh. Now that I"ve uninstalled it, I can get nearly two days of moderate use (streaming, built-in music playing, web browsing, video watching, etc). This is without the CDMA tweak as well.
When I was running stock, I noticed similar results, so it's not totally tied to me running a custom ROM either. Now, I'm sure they can tweak batterly life even more, and I'm looking forward to it. But, I get approximately the same amount of battery life with the same use as I did with my iPhone 3GS, so I'm satisified.
Moral of the story: if you're getting usually bad battery life, it could be a rogue app as well.