I have a 21 that's a few years old. It's pretty bulky for carrying, but the stopping power, as well as the slower muzzle velocity of the .45 make it worth it, I think. I only carry it when I'm hiking or hunting, and I keep it quiet because some people I hike with wouldn't be as comfortable knowing that I have it.
I'm a big guy, and I can make it disappear pretty quickly in a horizontal shoulder holster, but if you are built with a smaller frame, I imagine it would be more obvious.
Usually I keep it in my truck, easily accessible under the right side of my seat (captain's chairs). I carried it this way for years, then made friends with an FBI agent, who told me "if I was to give advice to my son, for instance, I would tell him to keep it accessible in his car, and not worry about carrying it". Things are pretty quiet where I live, and most situations here aren't going to be a "quick-draw surprise" kind of a thing. If you're awake, you should be able to see the need for a gun ahead of time. For the surprise walking down the street kind of stuff, I usually rely first on not being stupid enough to get into a dumb situation, then second on being able to react quick enough to escape. But, like I said, I live in a quiet town. If I moved, I would have to re-think a lot of this stuff.
My Dad had shot a .357 Blackhawk for years before he got his Glock, and it took him a long time to get used to the "Double-action-only" feeling of the longer trigger pull. So definitely spend some time getting used to the different feeling of the gun before you need to rely on it. For me, it was one of the first pistols I had really spent any dedicated time with, so I was able to adjust to it faster.
I'm interested in the subject of the conversion kits brought up earlier. I knew someone who had three or four kits he could put into one frame, but I've lost touch with him since several years ago. Anybody here have any experience with them?
-Travis