Since December 2004 I have been using a vserver provided by vlinux or my personal hosting. Its main purpose is e-mail. - Acting as my outgoing smarthost and dealing with my incoming mail (exim with clamav/greylistd/spamassassin and dovecot), which the small variant is just fast enough for.
All told I am quite happy with it, however there are some limitations.
Some syscalls are diabled e.g. the bind9-binary as shipped by Debian will not run which I sidestep by using
the evil dnscache instead) and I find
setrlimit(RLIMIT_NPROC) failed: Operation not permitted
in my logfile everyday.
The second big restriction is that I really only have got one IP, the public
one. 127.0.0.1/8 is not available for running internal services (like the
dnscache) on.