I just installed PandaHome, and I like it so far. The bells and whistles are nice, but mostly unnecessary to me. I don't mind the basic android them, not really looking to be bedazzled by the experience of opening my gmail.
I did this because I've had this odd problem with my home screen randomly going black. The notification bar is still visible. The icons, and widgets, while also black, are there, everything works. When I open an app, or even go into settings the program is visible like always, but for some reason the home screen goes black. I did a factory reset that seemed to fix the issue, but as I re-installed software, the black randomness showed up again. I thought it was toggle settings or locale, but both have been uninstalled and the black randomness continues.
Anyway, installing PandaHome, has, so far, alleviated the issue. I don't see much lag, but I've uninstalled a bunch of apps to try to speed up my phone. I've read that you have to keep at least 20-25mb free(on the G1) in order to keep it running without a lot of lag.