"An absolute no-no. Whoever first thought of putting soured cream on to a savoury dish must have been out of their mind. If you left that off you'd probably find your chilli does not need "jazzing up". It is a perfectly good dish on its own with your choice of pasta or (preferably) rice. "
I'm inclined to agree. The best way to jazz up a chilli is to use proper chillis (the ones that score at least 4 little chillis on the packet!)
I must say, while I like creme fraiche I would never put it on a chille con carne but the real no-no for me would be cheese. I love cheese, but it gets added to so many things unnecessarily,making them heavy and stodgy.
Best tip for rice is to drain the excess starch off first :-)