Black Majik--the very name means you belong to the Darkside.
The Prodigal Son has returned. Welcome home, brother.
45R, all the guns you've listed are fine pieces. My two cents on each:
I've handled the M&P Rich's talking about, and it's everything he says. After the trigger job, I wouldn't mind having one of those in my stable either. Only knock against it is it doesn't have Glock's track record. Yet. Same can be said of the XD, but time will tell. I'd say they're all solid designs.
I don't like the grips on HK's polymer guns. The USP is way too chunky for a 9mm. I hold high thumbs, so I don't like the fact that if I grip a little too hard, I can decock at the worst possible moment. My USP40 was a well made gun--neither the grip nor the caliber suited me, so I sold it long ago. Unless the HK45 is substantially slimmer, I'm done with HK polymers.
I have an SP-01 worked on by Matt Mink. I had the DA/SA turned into SA only (with the SA trigger), I had the safeties swapped out to the SA safeties for the bigger thumb shelf, and I had Matt do his magic on the trigger pull. After installing the comp sights, this is my most accurate 9mm gun. Cost me about $900 total, but I'd honestly put it up against any 9mm out there at any price--it's that accurate. Have not shot it competitively, however, so I don't know how it would do at speed yet. There are youtube clips of Angus Hobdell tearing through USPSA stages with his SP-01, however, so I'm sure it'll do well enough.
My Glock 17 is my comp gun. With it's simplicity in design and MOA, affordability, aftermarket support, fast resetting trigger, and it's uber-reliability, I see no reason why everyone doesn't own a Glock 17. Really. Oh, wait. Now Vu has one, and Rich, and Ryan, and Ken (soon). Nevermind. Everyone DOES own one.
And with good reason. (Really, the more I think of it, the more I'm convinced Glock's simplicity is the source of it's success. It just works. Everyone else's polymer entry just ADDS stuff like more stuff = better. KISS, remember?)
Get the Glock. Glock = MOJO.