Vacuum running all night? I've never seen it take more than a few minutes on my database, which isn't huge but isn't tiny either.
With 320MB of memory you can make the shared buffer pool about as big as you want, you've got a ton of memory! If you've compiled PG 7.0 with our recommended 16KB blocksize then -B 2000 will use 32MB, or 10% of the RAM on your box. On my own 256MB server I run -B 6000, i.e. 96MB and let AOLserver and the operating system file buffer and code etc use the rest.
