for most of the reasons you cite.

About 5 years ago I got a Nikon D40X with a 18-200 (not the kit lenses.) It's been great. My pro-photographer friends remind me that the 18-200 is a compromise (and they're right) but like you say, not having to change lenses is a really big deal for how and when I shoot. I was counseled repeatedly that the lens is actually more important than the body and in my experience that's been true. I'd do it again in a heartbeat although I lust for some low f-stop big glass to do my backstage photography where it's a combination of very low light mixed with kliegs and spots. The 18-200 struggles there but probably no more than most kit lenses.

The Nikon gear has been great but I believe the Canon stuff is easily as good, if not better, so I don't think it's a manufacturer issue.

We live aboard and I just have a small soft bag and it's held up fine. Having said that we have friends who've been cruising Panama for a few years ('Uhane) and he's got almost the same stuff that I do and due to the rainy season and humidity down there his stuff has been pretty much ruined. I'm sure he wishes he'd spent for an Otter Box (or equivalent.)

It IS pretty bulky. Having a point and shoot as well as a camera-phone has made that not a big deal though.

I'm no expert, just my very limited experiences. I'm in awe of the stuff posted here by Phil, Tom, Jon and others.