Get the Glock 20!! They are great guns, and you will not be disappointed with the 10mm round in the least!
I have a G20, and I couldn't ask for a more versatile weapon. With my 6" Jarvis barrel, it will run neck-in-neck with many of the factory .41 magnum loads, and you can download it to factory .40 power as well.
I think it would cost you about $90 to get a .40 conversion barrel as well, so you can shoot lots of cheap ammo at the range. This would also come in handy if there is ever a time that you can't get ahold of a lot of 10mm in a doomsday-type scenario or something like that.
The 10mm will cycle .40 in a pinch as well (with the factory 10mm barrel); it is not as reliable as 10 ammo and it is not the greatest thing you can do for your gun, but it will work if you need it to.
I had a Glock 31 (.357 Sig), which is the exact same gun as the 22 with the exception of the barrel (.40 vs .357). When I got the 10mm I was expecting it to shoot poorly (I was not yet used to the larger grip of the big frame Glock) in comparison, but all it took was one trip to the range for me to decide differently.
I shot the 31 in both .357 Sig and .40 (had a conversion barrel for that one too), and then shot the 20 with the factory 10mm barrel. I was very surprised that the bigger gun shot so well; I think Glock kept the power of the 10mm round in mind when they designed this weapon, and they did a great job. The larger frame and slide really soak up the recoil; it shoots great.
I have since traded the standard-sized Glock in for something else, but I will never give up my 10mm!
Oh yeah, and the 10 is not dead. There are more people shooting that round now than ever before. I have a friend that owns a gun store here in my area, and his 10mm handgun sales have increased substantially over the last few years. Don't listen to the anti-10 guys!