i really don't see a lag at all..i also double checked to see if there is one or not.....my buddy had a 3gs and wasn't jail broken we started the phone at the same time both came to the lock screen on the same time as well....then started hero of Sparta...loaded the same time as well...there literally is no noticeable lag...i have 16 gbs of music put on so my ipod is a bit slow but nothing bad or noticeable just chokes when i scroll through the songs i have...
as for the battery life...i really don't know if it's affected since the battery life isn't all that great for the 3gs
with cydia open and pandora in the background it didn't get below 130 for me. This is great finally we get to use it to its potential. Now i have to actually learn about all this stuff haven't had an iPhone in over a year.
still working great. I rejailbroke today using the latest goods and works great.
battery so far is good 17 minutes of use and 2 hours and 33 minutes standy still at 98%.
Ill report the battery when this cycle drains down should be around the same i would guess though. Everything is working good though love it.