For my first AR, I decided to build a retro-ish rifle. There were two problems: first, I'm left-handed, which means I really should find a C7 upper. That hasn't happened. Second, I'm a college student without the space or money for a bench, vise, torque wrenches, and everything else required to assemble an upper. I decided that an A2 upper really was close enough, and that if I find a C7 in the future, it will get swapped on. As-is, I'm pretty happy with what I'm calling my 'A1.5'. The rifle-length gas system is a lot more controllable than the M4geries I've shot in the past- unpleasant experiences with M4geries and their poor handling characteristics made me put off building an AR for quite a while. I love the balance and long sight radius as well, and the A1 furniture fits me like a glove. I'm 6'0", and the A1 stock LOP even works with plates.
The rifle herself was built off- a Del-Ton 20" lightweight kit I purchased during their Black Friday sale, with an Anderson stripped lower and original Colt or otherwise A1 furniture. Total cost before sling and magazines was just under $600. Reliability is 100% after 320 rounds of mixed Tula and AmEagle 55gr FMJ. Given as I just bought a couple of grips, handguard sets, and a stock on EvilBay, I think I may have contracted RBRD- a 655 clone might be happening this summer...