I've noticed, the companies I hear about going through YC now seem to progressed further along than companies in earlier YC sessions. I admit, this may be due to media reporting bias of covering companies that have product and traction, but I'd like to see some stats comparing YC companies by session and launch dates. I suspect we'd find that more companies being admitted into current sessions are already further down the development track than earlier in YC history.
Of course, this should be expected. YC has grown significantly, and has a ton of media attraction. It has become a signal of success, so YC has more applications from companies which are already seeing success and YC gets to limit their risk by taking on companies further down the track.