I compete at Engine Masters Challenge with the guys from IMM. They'll build you a great engine, but that is a different type of build - I doubt they would offer you a 50,000 mile warranty, or tell you 87 octane is OK to run at the weekend drags, etc. They'll build you a decent engine specific to your application, for sure.
Coincidentally, I work at BluePrint as an EFI tuner, and have some thoughts on the "complaints" here: the reason you read about complaints on forums is because of how many engines we ship - even if .1% of the engines have issues, having shipped over 300,000 engines out of our facility, there are a few engines with problems.
Build process - Our facility and assembly processes are ISO-certified, we do as much testing and QA inspection on parts as possible before they're installed- because we're not going to put a 50,000 mile warranty on a piece of junk. Sometimes we get bad parts from suppliers that slip through, in my time here I've never seen any customer being treated with disrespect or brushed off. I've seen a lot of engines that were covered under warranty with clear user-related issues (No, your smallblock ford doesn't like 58* of timing on pump gas). I have a hard time believing the few stories I've read about problems dealing with warranty claims. We have a lot of happy customers checking in, all the time. If you have questions about the product, ask freely. I'm a MOPAR nut, and engineer - not a salesman or advertiser. -Scott