This has been said before, but when installing the pivot pin detent/spring PUT THE RECIEVER IN A PLASTIC BAG. This will keep the detent from flying of to who-knows-where. I lost the detent yesterday and would be Very Sad today if I didn't have a spare in my spare parts kit. I would also say to break in not only the pivot pins, but also the bolt catch. Mine wouldn't tip up enough to catch the bolt and after reading the troubleshooting section I was worried that I might have installed the wrong spring. I lubed it real well with Tetra Gun Lube (which, I have to say, I really like), worked the catch a few dozen times and it works fine now.
If thinking about buildng your AR, all I can say is DO IT! It didn't take me long at all and the pleasure of knowing you took a bunch of parts and turned them into the rifle YOU wanted can't be beat.