If the tree fits your horse, then they are great saddles. I still have my first saddle, a Wintec 500 that is over 9 years old and is still going strong. I've had it on probably 5 different horses, but mainly my fat, fat, fat Arab.
I've found the older 500's have a flatter tree, while the newer ones (I also have one that is only two or three years old) tend to be more banana shaped. The tree can't be changed, only the gullet, so as long as the tree fits your horses back shape, then they work well.
I don't know where you live, but here in AUS Wintecs have great resale value, and as long as you paid a decent price you could easily sell it for the same (Or more, as a friend recently did) as you paid for it. I bought my newest Wintec 500 second hand about a year ago for $300 and could easily get that back again now.