I've read the kefir thread looking to see if anyone has tried it with heavy cream, and I don't see any info. I might have missed it, but I did a page-by-page ctrl-f on "cream".

I know you can do yogurt from heavy cream and it's excellent. Kefir... well, according to this lady's blog, it sounds like you'd end up with sour cream... which is pretty cool, IMO. I guess you'd just have to water it down or make a smoothie if you wanted to drink it.