OK, I'm gonna jump on this thread.
I did the Aprilia Demo thing at Chuckwaala Valley Raceway, and got to ride two 20-minute sessions on two different RS660s. One was bone stock, the other had an aftermarket tuned shock (Penske triple clicker, IIRC). The bike with the shock had also had tuned fork cartidges, but those had been swapped back out to stock before I got to ride the bike.
SO, my impressions:
The chassis is really good. The bike handles really well, and even with the stock shock goes around a track really nicely. The stock suspension is acceptable, but really, plan on spending money there if you buy one of these bikes. The aftermarket shock made the second bike much better.
The seating position is good, and I was OK with it even though I'm a big guy at 6'2". What isn't good are the pegs. Very slippery. I would have liked the clip-ons to have been spread a bit wider, too, but that's personal preference. YMMV. The seat's alright and the dash is current TFT, so I'm sure it can be set up how you'd like it.
The engine... Well, it has enough power to get around a track pretty fast, so don't assume it's slow. According to my source, it can deliver 90hp at the rear wheel with no internal work, 100hp with some work but still reliable. This sounds low, and sure- it's not an R6. But it's fast enough, and great for Lightweight Superbike club racing.
What really bothered me about the engine, though, is very little over-rev. Like a Ducati twin, hitting the rev limiter is like being smacked in the face with a two by four. The bike accelerates, accelerates, then bam! Party over. Redline is irritatingly low, too, so it kept taking me by surprise.
A side effect of this is the autoblipper downshifts just don't happen if you're up in the powerband. The bike won't allow itself to be shifted into those forbidden RPMs, so you can't simply slam down a couple of shifts going hot into a tight corner. You have to let the revs drop before each shift.
Obviously, that's something you just have to learn about this bike and a rude shock if you're coming off an R6 (for example) but not a deal killer.
Otherwise the powershifter worked alright, but again, the stock foot controls are not great and I accidentally shifted a few times when my foot tapped the shifter prematurely as I was setting up to shift.
I would buy rearsets immediately if I were to buy this bike. This is also true of the Tuono Factory and RSVF Factory bikes that I rode that day- slippery pegs and oddly set up foot levers.
So- my takeaway. Fun bike, a bit down on power and engine refinement compared to I-4 middleweights, but lighter and easier handling than them.
It would take me a while to get used to the motor and transmission's quirks, but I could easily learn to do that and have no issues.
The foot pegs and controls need to go- or at the very least, be adjusted and modified a bit.
The stock suspension would be acceptable on the street, but not great. For track use plan on spending that money.
I liked the bike and had fun riding it. A bit of work on it and some more saddle time and I'd be happy with it as my favorite track toy.