I bought a Walther p22 with the shorter barrel about 6 weeks ago and I think it is a great little practice gun. I have probably put about 700 rounds thru it so far with no problems. You must use high velocity 22LR though - when I first shot it I was using some CCI regular velocity stuff and I had constant failure to ejects and failure to feeds. Since going to high velocity I have not had a single one. As a sort of torture test I have not cleaned the gun since putting the 1st 200 rounds thru it - and it is still going strong.
As far as a target gun I don't know if it is quite what you want though - I can put 40 rounds all in the black at 7 yards - so it is pretty accurate - but I don't think it is at the level of accuracy of something like a Ruger MKIII or any of the other more target oriented .22LR pistols.
I have thought of using the P22 as a carry gun also - because I have gotten pretty accurate with it and because it is so small. You will get a lot of people saying that you should never carry a .22 as a carry gun - but the way I see it what you are doing is a situational thing. For instance if you are attacked by a meth crazed 300 pound ex linebacker you could probably empty all 10 rounds into him and not stop him before he got to you. On the other hand if you were held up by a 100 pound scrawny kid and you could plant a couple of rounds into his eye socket at 10 feet then dead is dead. What the research on defending yourself with a firearm shows is that most of the time just showing the weapon is enough to ward off an attack - in those instances where you actually have to shoot somebody - there are times when a .22 might get the job done - whereas a .40 or .45 is probably almost guaranteed to bring down the bad guy - if you can hit them of course.
If you think about using the P22 as a carry try one out with CCI Stingers - they make a bitchin' muzzle flash that might be enough to scare off any attacker without even having to shoot them.