Well, I just picked up a BushmasterXM15-E2S.  Nothing fancy, but it's my first AR-15 type rifle.  I plan on getting one of the SEBR too.  

Sorry no digital camera, but here's linky to Bushmaster...

http://www.bushmaster.com/shopping/weapons/pcwa2s20.asp

Just thought I'd share.  

www.bushmaster.com/shopping/weapons/pcwa2s20.asp

Good for you!

Do you plan to add anything, or just shoot it stock?

That was my first AR type rifle too. Get plenty of 30 rounders, USGI's with green followers, alot of ammo and start having fun.

Stock for now, until I figure out what I'm doing.  I found all the links to the Army manuals.  Stupid question, but exactly which one should I go to first?

I wanted something different form the SEBR, since I plan on getting that too.  

Well you do not really need a multitude of manuals, hell most of what we have on this sight is informational, look around. Good buy man, now buy some mags and ammunition for that rifle.

Quoted: That was my first AR type rifle too. Get plenty of 30 rounders, USGI's with green followers, alot of ammo and start having fun.

Got 2 pre-ban (I'm in MASS) 30 round magazines and a case of ammo.  Shot off a quick 30 on the way home yesterday.  Plan on going to the range in hour or so.  

Out of the five AR-15's I own, my Bushmaster A2 20" standard, same as yours, is the one that get's shot the most.  It's the one I most like to grab every once in a while at home just to sight down it for a bit.
Every time I shoot it, I find myself appreciating it's virtues more.  It still looks new, even though I only clean it occasionally.  It's been sighted in dead on at 100 yards for 3 years now.  All I ever did was zero it using bushmaster's own battlesight zero targets available on the websight, adjusted the front sight to be dead on at 100 yards (which puts it very near zero at 50 for me), and haven't had to screw with it since.
Great, great choice.  Chrome lined barrell will last a long time.  I almost always use XM193 in it, which it loves.  You'll treasure this thing until it's willed away to the next generation.