It's great to hear everyone's point of view with regard to Linux distributions. My own experience has only been with various Red Hat releases but I may try experimenting with a couple of others now.
As far as our project goes, we have decided to almost certainly use a hosting company rather than running our server, so if and when we get funding, we will either be looking at http://openacs.furfly.com or http://www.hub.org. They are the only two companies I am aware of that offer OpenACS hosting. I believe Furfly use Red Hat and Hub use FreeBSD.
If anyone knows of any other hosting companies that offer OpenACS, I'd be interested in hearing about them.