I've had a reasonable amount of luck with Arlington Automotive Machine and Charles Machine Shop both in Arlington.
Arlington Automotive has done the following for me:
disassemble, clean, and reassemble a Honda H23 head with a valve job
head milling
crank balancing
flywheel balancing
pressure plate balancing
A friend had Arlington do:
block boring & honing (Honda Civic and Honda S2000 blocks)
crank balancing
head disassembly and reassembly
The only problem we ran into with Arlington is they tore up the valve seals on a Honda D16 head when they reassembled it. The tool they used ripped a couple of the valve seals. They took the head back and corrected the problem. The D16 Civic engine that he rebuilt runs very strong. No problems at all with the machine work. Same goes for the S2000 engine. The owner cracked a ring land, so the block required honing. It's still going strong.
I used Charles Auto Machine for my current Honda head. He did the milling and a 3 angle valve job. He also did some misc. machine work for me. He's good at what he does, definitely. His main market is V8 guys, but it's a one man shop. He's the only employee, and you can see all of his equipment when you go into the shop. Impressive indeed. I plan to use him when I do my next race engine build. He only takes cash, though, and he's usually not as fast as Arlington.
Oh, Iain did use Charles to remove a broken stud from his exhaust manifold. Arlington said Charles was the only place in town that had the equipment needed to remove the stud without destroying the manifold. Sure enough, he had the manifold ready the next day, in better than new condition. :)