The only thing that really is different from the Jasjar rom is the O2 Active UI, and we all know that is very unstable.
Most Exec users end up using basic or corporate install, which is comparable to pressing the reset button after a hard reset and thus bypassing the extended rom setup.
I did no different then anyone else in that matter. I selected basic install. The Jasjar OS also is a tad newer, so unless you are a sucker for the O2 layout and style, I'd say stick with the Jasjar.
(I'm a sucker for the O2 styling so I will probably end up combining the Jasjar OS and the O2 ExtRom ;))
Just be aware: The Jasjar Extended rom will set your boot logo to the I-Mate one, the O2 Extended rom will NOT set it to the O2 one! It does not contain splash.nb files!