I've been thinking about doing this as it seems like a good compromise twixt gears and singlespeed.
Seems to me that a 32 chainring with an 11/28 cassette gives a ratio spread good enough to give you a good workout on the steep climbs but still pick up the pace a bit on the downhills. Drops a bit of weight aswell.
my second bike had 8 on the back for ages and it works really nicely - got me up and down pretty much everything in the peaks. my first bike is a singlespeed tho!
i ended up running one of them nasty dmr front mech things tho to make sure there was no chance of the chain dropping.
I've got a lovely dura ace rear mech sat around doing nothing so this weekend I'll convert the Zaskar to 8 soeed and let you know how it goes... I'll be your guinea pig
And yep, I ran inner tube on my DCD back in the day aswell!
mine wore so much i replaced it with a cotton wheel infilled with epoxy resin ... not exactly light weight...nor quiet....nor infact functional, but it seemed like a good idea at the time.