I beg to differ.
There are too many factors that are involved that will cause issues like this - a person's phone usage habits, the apps they have, the widgets they use, the settings, etc.
Then there is the ROM setup method used - restore from backup versus manually set everything up.
Then there is location - are you in an urban area with lots of cell traffic, or rural and lots of distance to a tower?
Finally, there is the fact that not all DROIDs are the same, even disregarding all the above-mentioned.
Some DROIDs like one ROM over another, whether it be because of hardware issues (or lack of issues) or whether it be because of a combination of issues above plus hardware, or whether it be because of even more factors, like Pete's being a vanilla GB ROM, which will have a bit more bloat and a bit less optimization than other ROMs being produced.
So, yes, it can very well be the ROM that is contributing to the problem.
After I rooted and I became an App Hoar, I found that stock ROms did not play nice with my phone at all. If I was not at leat OCd to 800 MHz (from 550 in the days of Eclair, and 1000 since) my phone lagged. Badly. I had this exact experience with Pete's more than a couple of times - OC'd it worked well enough, but it still never attained the level of superlative experiences I had with other ROMs.
At one point I had over 140 apps installed an was running a bare 15 MB free on my phone at any given moment. You put that into a GB ROM and I' be losing connections left and right as GB would start aggressively killing apps here and there, as it is wont to do, and I'd be in the same boat as him.
Pete is a fabulous dev, no unkind words toward him whatsoever - bu my DROID just doesn't like his ROMs with my habits and settings and such.
To each their own.