I have a DI as well (with an undervolt/overclock kernel) and while the stutters are quite short, they're definitely there. As an easy example, scrub left/right quickly using the optical joystick on the stock home screen. If you're looking for it or paying attention, it's not that difficult to notice 2-3 frame pauses elsewhere but those are intermittent so I assume they're GC pauses. It doesn't hinder my enjoyment of the platform, but when you're looking for something to criticize it's an easy target.
As for battery life, it depends entirely on where you live. I experimented on it for months before finally figuring out that well over 50% of the power draw on the system is the data network (mobile network option when you hold down power). If you have it on when you have really weak/no reception, the phone will burn through the full battery in about 4 hours and it's pretty simple to lose 20% battery in 15 minutes. If you always have a decent connection, your battery life will be fine, if you happen to live in a place where you have holes in your coverage (e.g. NYC urban canyons), battery life is terrible.
After realizing that, I set up a set of Locale rules to shut down the network when I'm on the wireless network at home/work and to shut it down when I lose signal. Combined with the undervolted kernel, I normally get 48 hours on a charge for my normal use (~350MB/mo).