I hope so. I am seriously hoping it helps with the lagging UI. I like what the Eris can do, but I think it just does it slowly--especially when dialing.
The dialing issue is something I've never experienced with mine. But I tend to delete my call history. I've read this helps, but I was already doing it, so I don't know if that's why. Then again, you may have known that already. If not, try it out and let's see if it helps.
As far as anything else lagging, the only time it happens for me is when I'm here in the hospital, in a section where there's absolutely no signal at all, including 3G. Don't know why that is, when I'm not trying to use anything that needs a signal.
--especially when dialing.