I've had my RC one piece for just about 8 years. I use Aerostich's back protector in it, but I don't use the hip pads. The suit was very stiff and uncomfortable for the first few weeks I owned it, but it grew into a second skin and is very comfortable now. I treat mine with wash-in Nikwax once a year and have never had a leakage issue. I think the best testimonial I can give about that is that I once made a run from TWO in Suches, GA to Tampa, on an FZ6, and had thunderstorms pretty much the entire way...I stayed dry as far as the rain was concerned (sweated instead). I did pay attention to how the suit folded.
Aerostich is now using waterproof zippers/tape in their suits, so I suspect the fabled "wet crotch" issue may fade into history. It's nice to not need to stop under a bridge to suit up for crap weather.
Since owning the Stich, I've not had a need to buy any other outer gear....probably saving me hundreds, if not thousands, of $$ spent on buying/replacing other gear over the last decade.
In terms of wear, my suit, while stained here and there, is still in excellent shape after 8 years of constant use. That being said, normal wear and tear still happens. The main zipper pull broke last year (the hook that holds the zipper pull just wore thru, easily fixed with a new pull from their suit repair kit) and the main zipper velcro, along with some other heavily used velcro, gave up the ghost. I finally broke down and sent my suit into Aerostich last week for an inspection, repairs, and alteration. They are replacing all of the worn velcro, retrofitting the waterproof main and leg zippers, and adding a little extra room in the mid-section (the beer keg's expanded a bit over 8 years, lol). While they're doing that, I'm putting up with a crappy 9 year old FS mesh suit I owned before getting the RC...can't wait to get my RC back. I should have the suit back in two weeks and fully expect to get at least another 8 years out of it.
On longer distance rides, year round, I wear the LDComfort tights and long-sleeved shirt under the RC, but I also use bicycle shorts and Under Armour shirts. In either case, fashion statements are made when I strip off the suit at a stop, lol. Evaporative cooling works pretty good with the sleeves opened up (I recommend removing V-Strom guards during the summer if you have them installed on your bike). It gets very hot and humid here in the SE and the RC never lets you forget that, but when you're running down the road, it's quite comfortable. In the winter time, I use a Warm-n-Safe jacket liner and sometimes throw on some sweat pants over the LDComfort tights, but have never needed anything more to keep warm (we do not get sustained, severe cold in this area). My daily commute totals about 40-50 miles, depending on the route I take, and the RC easily accommodates my work clothes underneath.
I've often considered picking up a two piece Darien/AD-1 combo in the belief that the 2 piece arrangement would add some convenience, but the reality is that the one piece has never been a problem and I'm very happy with it.