Hi Spondishy,
We've rented villas directly from owners many times and have never had a problem of any kind, but it is very difficult, if not impossible, to 'check them out'. You're not really afforded protection of any kind - it's very much an agreement based on trust.
You do need to make sure they have a local management company and that you are given contact information. I've never come across one which doesn't, but do ask the question.
I suggest you make a list of your requirements. When we first started renting villas, ours was pretty simple, but the more we go, the more we seem to find to add to the list!
Some things to think about, mostly picking up on what has already been mentioned:
How many are in your party? How many adults/children? How many double/twin rooms do you need? Invariably we travel with friends and we try to find villas with two identical, or very similar, master bedrooms. These are few and far between - most of those which claim to have two or more masters, have just one large master bedroom with an enormous bathroom. Subsequent 'masters' are often double bedded rooms with a much smaller bathroom.
Do you want a jacuzzi? Those with true spas (which can be heated separately from the pool) tend to be on the newer developments.
How important is it to be close to the parks? You will pay a premium for those closest to WDW. Those which claim to be 5 minutes from Disney, are genuinely 5 minutes from WDW <i>property</i>. As we all know, WDW is a big place, so the travelling time depends upon your destination within WDW. You will find, however, that only those in the Splendid China area of west 192 claim to be within 5 minutes of Disney. Those properties <i>are</i> genuinely the closest to WDW, so the 'times to Disney' quoted will give you a guide to their proximity. The link which edie suggests is the best I've found for working out where all the sub-divisions are located.
Do you prefer to be on a newer development? Do you want top-notch furnishings, or just somewhere clean and comfortable? Is cost your key concern?
What time of year will you be going? We pay for pool heating whenever we go (as we always opt for a jacuzzi - not much point having it if it isn't heated), but you will definitely need it outside the summer months.
Check out whether the pool area is overlooked. This factor doesn't seem to make any difference to cost. We tend to go for pools which overlook lakes or conservation areas. At a push (if everything else was exactly what I was looking for) I would accept one with a fence, but I can't imagine staying in one which backs onto the road, or onto another villa.
Do you have to travel to pick up the keys? This might seem like a minor detail, but after a 9 hour flight, it's quite signficant. We once stayed in a villa on west 192 and had to collect (and return) the keys from an office miles east on 192. I will <i>never</i> do that again. Try to get one which has a key-pad at the front door.
New developments are springing up all the time. I used to think I'd got a handle on it all, but I'm starting to lose track! I've got literally hundreds of villa sites saved in my Favorites, so if you post with some of your requirements, I can probably pick some out.
Finally, you do get what you pay for. Does the price seem right for the location, time of year, amenities, standard of furnishings?
why you ask, well it gets too hot. When outlaws were buying theirs (one of which is south facing) they were warned that a few people have even died from staying too long on their sun deck
It also has TVs in 3 bedrooms and in the lounge. We have used it 2 years running and have already booked for next July. 
