It's hard to judge reliability on an internet forum. People are much more likely to make a thread about a problem they had than a "Rode all week without any problems" thread. But, I do agree, seems like we see a scary number of costly failures on the 1700's on the forums, as compared to most other Vulcan models. It almost seems like bikes are outgrowing themselves. I frequent a handful of motorcycle forums (or skim them). Seems like the big Harley twins (96 and up), and other big metric twins (various 16, 17, 1800+ twins) seem to have a lot more problems compared to the sub 1600cc category. Those 88" Evo Harley's seemed fairly bullet proof compared to their previous engines, but then they headed downhill again (in my perception) with the 96" and 103" motors. More power means more heat, and perhaps, these components can't get rid of heat quick enough, or just can't handle the power these big motors make. Who knows. (Although, the Vulcan 2000 seems to be another dead reliable gem, judging by these forums anyway!)
I was in the same boat as you a while back. But, the more I thought about it, the more I realized I really did enjoy touring on my 900. There are things like cruise control, lower rev's on the highway, and the like that would be nice, but nothing wowed me so much to justify spending a whole bunch of money. Ended up getting the Shadow for the wife! We've got a bluetooth headset, and hearing her tell me "There's nothing in the world like this!" as she's riding in front of me on her little red shadow really affirmed that decision. Mushy I know, but watching her enjoy the joy of her own ride is worth all the electronic cruise controls in the world!
I'm in the process now of just building my 900 into a big touring bike. Most recently installed a Harley tour-pak. That's much bigger than any of the aftermarket trunks on the market (that I'm aware of) for the 900. The weight added over the rear really added some stability to the bike. It was already solid, but now it really feels like a big bike. Big bikes aren't stable in the wind and on the highway because of their horsepower, it's the weight and size of the bike. The 900, despite the small motor, is already the size of most big twins (in terms of the size of the bike itself) and is only INCHES shy of the dimensions of the 1700, or the big Harley tourers. The high RPM's don't bother me, personally, and I've never felt limited by the 900's power because I don't ride 80+ anyway. I've pulled some serious hills, in top gear, at 65 no problem. Having owned a couple manual transmission cars, I'm used to downshifting on the steep hills at a lower speed, so that doesn't bother me either.
Moral of the story, if you aren't sure what bike you want to upgrade to, don't discount what you've already got. Not saying the 900 is the greatest touring bike ever made, but it is certainly more capable than people give it credit for. I still have a smile on my face on 500+ mile days on my 900! The future plans for my bike include a stereo fairing (or adapted Harley fairing) and big hard bags. My thinking is, whatever bike I move up to next (and I eventually will, I do love my 900 but a big twin is in my future in the next several years I'm sure), I can simply transfer those touring goodies over. Rather than buy a voyager (if I go the 1700 route), I can just go with a Nomad (for the cruise control, otherwise I'd just get a 1700 Classic!), add my tour pak and fairing, and go! If for some reason I went the Harley route, I could turn a softail or road king into a full dresser. And so on and so forth.
That's the plan anyway! Good luck with whatever you end up doing. If you have any questions on the shadow send me a PM and maybe I can tell you what I know. I've done some research on them before I bought one and, well, now I own one! Wife's is a 2011 Aero, and she loves it. It's great for a new, shorter rider.