I agree, on painted areas of the cars they do not seem to work all that well, and I continue to use good fiber towels there.
Having said that, I have 2 cars that have chrome rims on them, and one of the sets is a pretty intricate design. It's always been hard to get the water out of them (short of using an air compressor), but I cut up a sham wow and use it on the rims now. It reaches into the nooks and crannies where the water has pooled and sucks it right out. No more driving 2 feet and having water spots all over the rims!!
I also find them good for cleaning and waxing the rims too, like goat said. It spreads wax nice and even, although I think you waste a fair amount due to absorption. At least it seems like that, as the used rags end up being much heavier than when you started.
So my rating of them is good for some jobs, but mostly useless for overall car work.