I've rented points for 3 stays now - all through David's Vacation rentals - and it's been a uniformly seamless experience. We don't mind the lack of housekeeping (I actually appreciate the added privacy and the chance to nap in the afternoon with no fear of an interruption), and we plan our vacations more than a year out with no changes in dates, so the lack of flexibility is okay with us, too.
In short, I agree with everything
@CaptainAmerica mentioned in his post, although for my family, the things he mentioned as detractors are either positives or non-issues. I would, however, qualify his comments about savings. The amount of savings depends on the room category you're booking. We've only rented studios (at the Polynesian and Beach Club) or 2-bedroom villas (at Wilderness Lodge), and have saved 40-50% off of rack rate for those accommodations every single time -- far more than we'd have saved even with the most generous room discount offer -- even though we've always booked at 11 months out and therefore paid a "premium" rate. Those who rent 1-bedrooms, however, only save a little, the way the points are calculated.
We've loved renting DVC points, as it has allowed us to stay at deluxe hotels on a moderate budget. We do purchase vacation insurance to cover the costs when/if we have a longer stay or are traveling with other family members, given the non-refundability of the price.