Here is my personal experience, again YMMV... I have found that on the Droid, GB is going to be a very fickel beast. It is very aggresive at freeing up memory, which would explain most of the issues that some are having (it is the reason you have to keep the messaging app in memory to get texts). Now with that said there are various ways that we can help our little Droids run GB.
First and foremost is to find a kernel that will allow Compcache (currently the only one I know of for sure that will do this on GB is the stock CM kernel that was modified by Prime). Once you enable compcache most of the memory issues should go away.
Some other things you can do if your ROM allows it (CM7 allows these things, if your ROM doesn't I would suggest Root Tools by JRummy from the Market):
Set your VM heap size to something large (I currently have it set to 32m which is the highest you can go in CM7).
Set your Compcache RAM usage to something high as well (again you need a kernel that will support this in GB or the setting wont do anything) I have mine set to 26%.
Always make sure your home app is set to be locked into memory in both your settings and the settings for your home app.
I hope this can help some what, I am really enjoying GB and I hope that once we can figure out how to work around the memory restrictions on the OC Droid that everyone can. Now I do know that every Droid is different and there was at least a few people I know of that couldn't get any Froyo ROMs to work on their phone. However I'm hoping that we can at least get some of the kinks worked out GB IMHO is truely a step up for me.
For the modified Prime kernel and more information on the Milestone OC application (which is AWESOME BTW) follow the link below:
[Tut] Milestone OC Application [Tut] - Droid Forum - Verizon Droid & the Motorola Droid Forum