There are some awful good AR-15 makers nowadays, the Les Baer rifle looks pretty good to me but truthfully most of the higher-end models from the major mfgs are pretty good. Colts seem to hold their value the best, some of their older rifles were pretty nice.
I had mine out shooting yesterday, I have had it for about 12 years or so. It is an Olympic Arms Ultramatch, with 24" broached barrel, Williams set trigger, hard chromed bolt and hardware, all the goodies. It has an old-design flattop receiver, basically they milled off the top back then and put on a Weaver rail. I have a cheesy Tasco varmint scope on it and it is actually a pretty nice scope, on a calm day the rifle is capable of well under 0. 5" groups - in fact, the Oly Arms guys used to have a "1/4 MOA" club for people shooting these rifles, with a good AR-15 this is more common than folks might think.
People who haven't shot one of these target-style AR-15s don't know what they are missing. Very low recoil, even from a bench, and fast reacquisition of the target make shooting these rifles almost like putting a laser beam on target. I never would have thought an M-16 platform was capable of such accuracy... until I actually tried it!
Things to watch for: The AR-15 chamber has bolt locking lugs on it that incorporate small feed ramps. Due to the bolt geometry, the lugs are fairly square and sometimes have sharp edges or burrs that can affect feeding. Chamber a single round in the rifle you are looking at, then eject it and check out the bullet - if it has been heavily scarred on its trip into the chamber, accuracy and reliability will both take a hit. There are a lot of people with wrenches and vises who fancy themselves "AR-15 smiths" and put together "custom guns", if you buy one of them check it over carefully and make sure the gas tube and barrel etc are mated correctly. AR-15s are pretty darned simple rifles, but people still manage to dork them up.
Usage tips: If you haven't fired one before, sometimes you will notice a loud "sprrroiiinggg" in the stock, it is just the sound of the buffer spring resonating and is nothing to be concerned about. The rifle is very easy to break down and remove bolt etc from carrier, however frequent removal of the pins will eventually "wallow out" the holes if you are not careful. On the AR-15, the "less is more" philosophy of lubing is the one you want to follow. If the rifles upper/lower receivers do not mate tightly, they sell small rubber/plastic wedges called "accu wedges" that tighten them right up no muss, no fuss. Good magazines are crucial to perfomance if you shoot a lot, some have the so-called "Green follower" that has longer legs for improved spring guide geometry and less risk of jamming.
A properly set up AR will not jam unless you have done something screwy with the magazine or have some bad ammo, they are very reliable rifles. I ran 60 rounds through mine yesterday without a hiccup...
Attention: TDR Forum Junkies 
I do think I will try one first on my AR, I have a nice 30-06 for the long range shooting I need to do so something that will work at 100 yards is right what I'm looking for. I've also been looking at the various hollow (spelling) sites out there as well trying to deside on what I would like better. 
