I've set myself up a NFS account to test it out on one of the blogs I host. A few first impressions:

- things are a little quirky (such as having to choose a unique "short name" for a site, unique across all of NFS's users)
- every site gets it own ssh login, with a very long user name
- can't use A records to point at the site, only CNAMEs (their load balancing system means IP addresses will change)
- no cron, which is a pain for database backups, I'll have to code an php page to call each day before rsync'ing my backup

Performance seems to me more consistent than dreamhost, most blog pages are taking ~0.5 seconds to run, as opposed to 0.2-5 seconds on dreamhost.