nginx reverse proxy on separate vps

I've read about people running apache on a nonstandard port, and setting up nginx on the same box to proxy requests listening on 80. I want to do something like this, but with the reverse proxy running on its own, separate VPS.

My thinking: I'm deploying what I would like to be a scalable, high-availability web app. If I have to take the main server down for maintenance/move/whatever, or if it goes down on its own, I can display a friendly "check back later" message to users instead of their connection timing out. Also, if I had to set up load balancing down the line this would make it easier.

I would get 2 linodes in the same datacenter, and use the private IP feature for traffic between them. My only concern is, would shuttling the requests between two VPS's incur a performance penalty? Any thoughts?

I'd probably be running nginx on both nodes, if it matters.