Modern 1911's are some of the most reliable, if not THE most reliable, semi-auto handguns out there.
As a 1911 fan, I will say that a well put together 1911 with quality components will be quite reliable. Though unfortunately with so many people making them, there are a considerable number of factory built and buba'd turds floating around out there.
Maintenance on most 1911's require the use of a tool (bushing wrench) and are a bit more complicated than your beretta/glock/xd/sig in the basic disassembly for cleaning -- however, once you get used to it it's only marginally more complex
The bushing wrench is need for most models equipped with the full lengh guiderod. Keep it simple (GI-style partial length guidrod) and other basic, GI-style components and you can
detail strip the entire pistol using just your hands, it's own parts and a 45 ACP cartridge (to unscrew the grip panel screws). Pretty engenious design, really.
1911s are pretty easy to field strip, though not as simple as a Glock or XD. Then again, you don't have to pull the trigger of a 1911 as you do on a Glock or XD (XDm excluded). And though I've never detail stripped a Glock or XD, most that have agree that detail stripping a 1911 is far easier.
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As for the GP100, it is an excellent revolver that will give you years of enjoyable, reliable service. Though you did state you were looking for a gun in 9mm or 45 ACP. Anyway, the GP (available in 38 Spl or 357 Mag) make exellent nightstand guns as well (long, heavy trigger pull, no safety, no slide to rack). Though I'd handle a S&W 686 as well, which I myself preferred to the GP. While your looking, you might as look at other classic Smiths, from K Frame Model 19s to N Frame Model 27s.
And if you are interested in 45 ACP, you might look at used N Frame S&W model 25s and 625s.