I've had 2 Designers and a Pinnacle. The first one I owned wasn't new, so it doesn't count. The second Designer I bought was a 2008 Designer (35 ft long 3 slide, don't remember the nomenclature). While it had issues Jayco was good about getting them fixed. I won't say it was trouble FREE........but most of the problems I had were from normal wear and tear.
My last trailer is a 2015 Pinnacle 36REQS. I bought it 3 June. And it has ISSUES. However, I won't go into them here, as, so far, while I haven't been able to take the trailer back to where I bought it for service (just too far to travel) I have taken it to a close Jayco dealer and have been satisfied with the work they've done so far (it's back in for more warranty work for different issues). I have been on the phone with Jayco's customer service, and they SEEM to be working to help me get my problems resolved. So right now I'm holding judgement and details of my problems, until some kind of resolution has been reached.
Would I warn you off a Jayco? No. I don't think I would. The ones I have had, mechanically, have been built like tanks, and have performed in very harsh weather most satisfactorily. HOWEVER. If you DO buy one, I wouldn't get too far from your dealer untill you've had some "shakedown" cruises close to home, so to speak. You're probably going to have some kind of issues. These are fairly complex systems, and a CERTAIN amount of bugs are probably normal.