I went to a gun show and was amazed at all the uppers and lowers there, and variations of complete guns that were for sale (this show happened to have many more than most shows).

Does anyone tinker around with these? Do you suggest buying a complete gun, or an upper and a lower?

Depends on what you want and if you want to mess with it. My first two were complete gun purchases because what I wanted was available in a complete firearm from a maker I wanted. My third was a build. I wanted a black Tefloned stainless steel lower for the weight and did the build myself on the lower, then bought the upper in .458 SOCOM from Tony Rumore of Tromix.
Depending on your desire to do it yourself, you can save a little money buy building the lower yourself and believe me, it is very easy and requires only minimal tools. The upper is a little more trouble and you need more tools for an upper build, but you can learn a lot and have a lot of fun (and frustration) doing it yourself. If I can find exactly what I want, then I prefer to buy a complete firearm, but if I cannot, then I'll do at least the lower myself.

Correct me if I'm wrong, but can't you also buy a complete upper, and a complete (or bare) lower?

Then just put the 2 halves together? Can you actually save much doing this, or do you have to buy a bare lower to really save anything?

I'm not even convinced that I want an AR, but if I did it would be something pretty easy to find already built I think.

yes you can

To learn a lot more about the AR15 and it's variants, try AR15.com, or one of the several excellent books on the subject.

Crazyquick
If you want best accuracy, I would suggest a Frankengun built from parts. It's not much more expensive than buying the factory built accuracy models and you will notice the difference.
If you are looking for a self defense, hunting, general use gun then mix and match uppers and lowers
will still generally meet your needs. Armalite,Colt, Bushmaster and Rock River are good brands.
American Spirit is a brand that has been much maligned, but I built a very accurate NRA Service Rifle off one of their lowers and have been very pleased with fit and function. I probably wouldn't buy a complete rifle from them, however.
good luck
Covey16

You really should check out www.ar15.com before buying an AR.

I just bought my first one as a complete gun, with the 16" heavy match barrel.

I say first one because after 1 range trip I am sure that at the least I will by a couple of additional uppers and maybe another complete weapon.

I shot 5 - 5 shot groups @100 yards with 3 different kinds of ammo and got the last 2 down to 7/8" with iron sights. The first one was the largest at 3", which I thought was good for a brand new rifle.

Can't believe I didn't buy one 20 years ago, this is the best shooting firearm I have ever gotten right out of the box.

I agree that you should visit AR15.com, I spent a month going through the forum before I made my purchase. There is some great info there, and apparently some very experienced AR shooters.

I had glanced over thier forum, but was reluctant to register for (another) forum when I'm already a member of so many, know what I mean?

I was hoping to get some comparisons between brands from here, but I guess I'll have to go over there. Oh well. Might shoot a friend's Colt (pre ban, thin barrel, A2 sights I think) this weekend, which is the only kind I have expirience with.

Build it Build it Build it Build it! Very easy to get yourself shooting a AR post-ban for $500 or less with some shopping. i have several Colt, DPMS, RRA, Bushmaster, both pre and post ban. my favorite is a M4 clone i built from a [$86] DPMS lower and [$399] kit with 16" heavy barrel, float tube and flat top upper. it shoots 3/4moa out to 300yds with Winchester 45gr white box ammo. if your gona own a AR you need to be able to keep it running anyway so you may as well build it from the get go.
as others have said the AR15.com bunch are a mostly DICKS these days.

Depends on what you mean buy "building" and "kits". It's usually cheaper to buy a complete lower and a complete upper, than it is to buy a whole rifle. A monkey could assemble the two halves, it's two pins.

If your talking about buying a stripped lower and upper and all the parts, that's a whole other ball game. Not REAL hard at all in the world of gunsmithing, but beyond many people.