If I didn't know better, I would think this thread was started by one of my good friends - lol! He is the type that ALWAYS has to have at least a few guns "out" being worked on, modified, converted, acurized, etc. I know him for 27 years now and I can not honestly think of a time he actually did not have something in the works.
He has had some success with different services, Gun Smiths, etc. but 50-60% of the time has had nothing but problems, shipping issues, shipping damages, poor finishes, push off, light primer strikes, poor B/C Gaps, jamming, misfeeds, damage to things that were not damaged prior ,etc. To make the situation even sadder, he mostly spends more money on the mods than if he bought a gun that he wanted to turn it into in the first place!
While we all (his friends) realizer his "joy" is to always fiddle-futz with guns (does same things to other stuff he owns), it is usually counter productive, costs him way too much and he's only satisfied less than half the time. HEY, if this is fun to him or anyone else - far be it for me to stop anyone, but I find that in many instances, this is the case.
I guess many here have had success or have done the work and mods themselves. If someone is fully capable, has all the tools, the know-how, time and patience - then I say go for it. For someone who does not even own the gun yet and wants to buy one he doesn't like in it's current condition - it seems silly to me to do that and send it out, spend money and pray it comes back perfect. Again - just my personal opinion.