Just out of curiosity, why did you go with Slicehost instead of Linode? For Rails hosting, RAM seems to be limiting factor if you only want to spend $20/month. On a Linode 360 I'm running 3 mongrels, nginx, and MySQL with some RAM to spare for crons and such. I'm just curious what advantages a Slicehost 256 would give me considering RAM seems to be the main difference between the two.
I've been using linode for the last 8 months and so far it has been a wonderful low cost, high performance solution. My only complaint is that they don't appear to offer any backup solutions. I an under the assumption that I'll be rebuilding my linode disk image from scratch if the physical server is involved in a fire, corrupts my disk image, etc. It would be nice if I could do the equivalent of take a snapshot, encrypt it, and upload it to s3.