We have 3 Don West saddles. They are extremely comfortable for long days in the saddle. I've never had a sore horse or any complaints from our girls. I did have a tiny problem with a small dry patch at the withers of my low withered Vida. I've since got a different pad and solved the problem. It was more an aesthetic thing with me, she was never sore.
So far they are fitting all 4 of our Rocky Mountain horses, which have a slight build like the Paso's. I do prefer a saddle without a horn so think hard about how much bending under branches you do before you get one. We have 2 with a horn and one without, we fight over who gets the hornless
All of ours are older models before he started making a production saddle. I can't comment on the newer ones as far as quality goes. I know they have gone to a synthetic fleece instead of real sheep's wool like the old ones. Besides that I don't know what other changes they have made as far as leather or construction quality. Don is a great guy to talk to so I'm sure if you had any problems he would make it right.
ETA: Check to see if whoever you buy it from has a trial period. Many manufacturers have a 2 week or so try before you buy guarantee. I've done tons of research on gaited horse saddles and to me, for the price, the Don wests are the one of the best. The only thing I wish his had was a Texas or 3/4 rigging options.
Don bred Peruvian's and built this saddle specifically for then so I'm sure the fit will be great.