We have no regrets - we own enough points at VGF (bought direct) and BCV (bought resale) to stay a week in 1 BR every year (i.e. alternating). This use year we used our points to stay 5 days in a studio at VGC, will have 1 week at BCV for F&W, and will be using our points to stay at SSR for a "last minute" trip in January.
1) People regret
DVC I think if they buy the least expensive resort expecting to switch to a more popular resort at 7 months: we own at BCV, I booked our week at month 11, and in month 10 there was no availability to add on an extra 2 days for F&W.
2) People who buy into DVC need (to a certain degree) to be able to plan way in advance if you want to stay at certain resorts: we booked our F&W trip at 11 months and "last minute" (see above) means we planned a trip in August 2015 for January 2016. For January, there was no availability at the monorail resorts, the EPCOT resorts, and very limited at AKL. OKW and SSR had availability so we are staying at SSR. If you buy expecting to book at your home resort with short notice, there might not be availability: we own at 2 popular resorts but lost the booking advantage due to when we booked. It is what it is.
3) DVC is not a luxury hotel. You do not get room cleaning every day.
4) Don't buy DVC for any perceived perks: AP discounts may come and go, TiW may come and go, trading out may change, etc. All you are guaranteed really is the ability to stay at your home resort and have a booking advantage over non-owners.
5) People regret it if they don't understand the terms of the deal, like use year, booking windows, how to borrow/how to bank, banking deadlines, etc.
DVC advantages (and this is subjective, so these are advantages for us):
1) No more discount roulette: I used to book a room then sort through discount A and discount B and call to get discounts applied to the reservation. It was a pain and I frankly don't have time to play that game. Now I book and we're done.
2) We get a 1 br with a king bed. We used to pay an insane amount (to me at least) for essentially a studio at a deluxe resort (we would stay at GF or YC pre DVC) and now we get to stay in what we feel is a nicer, bigger room at either BCV or VGF.
3) No daily housekeeping - this for us is an advantage.
4) We know we will be back - so much less of the "we have to do everything" frenzy.
5) In room washer and dryer - I underestimated how handy this was for us in a 1 BR. We use this way more often than I would have guessed when we bought in.
edited to add: I'd suggest looking into resale (but again know the differences of buying real vs direct). We bought BCV resale and VGF direct (right when they started selling it). As a side note, other posters have mentioned outgrowing Disney, we're a 40ish, childfree by choice, professional couple and love Disney because its easy: get car service from the airport, walk or use disney transport once on property, eat/wander/shop/ride when we want, hit the pools, and relax when we want. Its an easy vacation for us that requires very little actual planning.