I just slapped one together from a $300 basket case plus some parts I "borrowed" off another Luger, and it worked fine right off the bat. I have another "mixmaster" I bought complete, and it took quite a bit of troubleshooting and tinkering, but it works great as well.
I don't think they're better than matching guns that has been fitted and put together by the factory (that kinda goes without saying), but you can build a reliable shooter if you just take your time and pay proper attention to how it works.
If you buy a mixed parts gun, you are taking a chance. You never know who put it together or how it was done, and I have found the most amazing jury rigs in some project guns I have bought. I'd recommend that you take it apart completely and check it. Just a few hours ago, I found that the toggle bolt in my basket case was made from an old hardware store bolt, and it wasn't pinned in place either. And speaking of pins: I don't know how many home made pins I have found, made of baling wire, nails or whatever the "gunsmith" happened to have handy at the time. But that's just part of the fun.
