Putting an AR together really isn't that big a deal. While I am pretty practiced at it, and have some specialized tools, after laying all the parts out, I can slap a lower together in about 5 minutes. I highly recommend getting a few good manuals, and the big poster bushmaster sells with the exploded parts view. Since the start of the year a lot of bare lowers have been coming into california. Both working at the range, and working as a gunsmith I have assembled, reassembled, repaired, and refitted a lot of guns that were not put together right.
Things to remember:
1) If you have any left over parts, you did something wrong (one guy didn't put in the disconnector spring, so it was full-auto)
2) If you are having light firing pin strikes you put the hammer spring in backwards
3) There are several types and sizes of pins, there are roll pins and detent pins, they are not interchangeable
4) When putting in the grip screw, put it in first with the grip off, this will "chase" the threads and will make it easier to get your grip installed without cross threading or stripping (lubricants help this effort greatly)
5) After you have put the lower together perform a function check. This involves putting the hammer in the "cocked" position, pull the trigger and ease the hammer down. Keep pressure on the trigger, now push the hammer all the way back, removing your hand, slowly release the trigger, it should snap forward slightly when the disconnector releases and it is then caught by the sear. Repeat this test several times. If it fails at any point, you have done something wrong, review your diagram, take everything apart and do it right.
6) When assembling certain parts you need a tool called a "roll pin punch" (this is especially true for the roll pin that holds in the bolt catch) This will make your life much easier, and will prevent you from scratching your reciever.
The AR-180 is a very different beast from the AR-15. In some ways it was a more advanced system. It was also designed by eugene stoner as an answer to some of the shortcomings of the AR-15. In my opinion it is a very nice firearm. I'm not sure if it truely provides a better answer, since in my assessment, the AR-15 is a damn good rifle. But, it does have some advantages. If you are still looking at the AR-180 platform, you may wish to check out the robinson arms family of guns. Thier products are loosely based on the AR-180, but they have some modifications that they have done.
I have fired the robinson arms versions in full auto, and they are probably one of the nicest handling full autos I have had the pleasure of playing with. They are equally nice in thier semi-auto counterparts.
If you are looking for an AR-15 series, in my opinion the nicest lowers are made by Mega (gator-15) and SunDevil (SD-15) these usually retail for under $200 (at least in cali) and are made by machining solid blocks of aluminum. The fit and finish on these is impeccable. Otherwise, I might recommend the Spike Tactical, I have seen these for as low as $100. As far as I'm concerned all of the forged lowers are created equally, why pay more for one?
If you add to that the lower parts kit ($50-70) and the stock ($30-100) and an upper (~$500-600) you can put yourself together a nice rifle for about 7-800 dollars.
So far I've had the best luck with STAG uppers. They are fairly low cost, and easily as good as the more expensive parts offered by bushmaster. (I've owned both) The one that currently concerns me however is apparently Model1sales (another provider of parts) has been having the bolt crack where the cam pin goes through. I'm not sure if this has been addressed at all, but I have heard of at least 5 instances, and seen 3 personally. But they do offer very competitive prices on parts... So Buyer beware...
), or do I have to get an Ameetec upper?
. Outside of Cook County, and some other little towns who's names I cannot remember they are good to go.........for now. 
