Machine built wheels can be as good as any if the manufacturer lets the machine take the wheel to near it's max tension. More can be built if the final tension is lower, ergo the cheaper ones are not as well made.
I like the Gerd Schraner method of spoking the wheel. The pulling spokes have the heads inside the flange. According to Mavic it makes for a little stronger wheel.
If the tension on a new wheel is low it makes sense to raise it, but not untension it first.
I have built, rebuilt and repaired wheels for friends since 1993. I have built at least 20 since then. Normally I don't have problems. The exception was a friend who weighs 225 and is as strong as an ox. He bought a Power Tap wheel built up with an Open Pro rim that he cracked and broke the replacement. They don't make that hub in a 36 so I got a Sun CR-18 rim and tensioned the drive side to 130kg. The only problem he had was when he dropped the chain into the spokes and cut a few.
If you can true one you can build one. Just take your time and get the right tools. I have a Wheelsmith tensiometer, a Minoura truing stand and a cheap dishing tool. I could get by without the last two, but I think the tensiometer is the necessary tool to have. A spoke driver is nice to have and a spoke wrench you are comfortable with.