Fortunately, more ram can usually make up for slow disk.
I am working on a zfs based network storage system that just might solve the problem and then some, but it's not anywhere near ready yet.
Slicehost does however have very nice and useful articles and it is nice to support them if you use those.
Keeping an OpenVZ VPS running smoothly requires a lot more SysAdmin attention than keeping a Xen VPS running smoothly. The Johncompanies people, last time I tried them, were excellent.
This is really interesting, I'm wondering if you can elaborate a bit?
I'm reasonably familiar with OpenVZ and other "container" approaches (zones, jails).
It sounds like there's a missing abstraction layer, or maybe just fewer administrative tools for these container approaches than the built-in-at-time-of-creation attributes of a true virtualized guest.
Just guessing, but I'd expect disk access is a bigger bottleneck on highly loaded VPS servers than the CPU, so the worst and average case disk performance are probably what would concern me the most. I think prgmr is a fantastic deal - I certainly haven't seen anybody else offering so much RAM at that price point. I'd be a customer if they were located on the east coast.
Finally, for those who don't know, prgmr is owned and run by lsc who's a member here:
http://news.ycombinator.com/user?id=lsc