Don't have all the answers, but here is what I believe to be true.

According to the information discussed in a URC class, all 3000's manufactured after April 1, 2005 have narrow band antennas. If you have the small USB connector, you have the narrowband antenna.

In the latest URC Price Book, the 3000 is listed as available in 433 (3000i) and 418 models. (Dated Aug. 1 2007)
The difference is the operating band, the real world impact depends on the area of your installation. I have not used the new i-series 433 band URC remotes.

Battery life is really installation dependent, I use a 20sec backlight time for programming and no one has complained about battery life so far. . .

I believe we will see an upgraded 3000 with two way communications in the next 12 months, that's about all I've heard.