Quoting myself from the other day:

'’It actually seems like Plone 2.5 can run on a machine with only 256Mb of memory with acceptable performance as long as the CPU is fast.’’

Very wrong for my instance. At least if there is anything else running on the machine, in this case a mail server (Postfix+Dovecot). Sloooow..

Resized my slice from 256M to 512M. Seems to work better now.