Is anyone running 10mm?
Had any problems? Recommendations?

I've been looking to get one to go with my 10mm pistols

I don't have one.  I'd like one if it took Glock 20 mags.  

I sent an email to Lone Wolf when they came out with their Glock mag capable 9mm/40S&W lowers.

They replied they have a lower in the works that will take G20/21 mags.

Rudy at Macon Armory has been playing with a 10MM DI upper, might touch bases with him.

I have a Glock Model 40, 10MM, with a Burris FF3 mounted on it.
Shoots great, takes the G-20 magazines as well.

It shoots very, very well.
Prior to putting the FF3 on it, it,as typical Glockish for me, shot to the left a little bit.
After putting the FF3 on it, it shoots great.
I did a bench rest shoot with it, and at 25 yards, it shoots around a 2 to 3 inch group, depending on my wrist and the rest.
At 50 yards, it shoots a 4 inch group, +/- an inch.

Amazingly, at 100 yards, the group is around 10 inches, in a tight rest.
Pretty scary for a handgun.
I took it to a qualifying shoot for the PD, and let the other guys shoot it, and at first they were a little intimidated by the "10MM" aspect, but that wore off quickly.
I think at least 2 of them own the things now.

I carry it out in the woods in an Alaskan Ultimate Holster, definitely not on duty.

While not technically an AR-15 I have been looking at one of these.

http://www.tnwfirearms.com/product-p/asrx-cplt-xxxx-xxxx-xxxx.htm

If In can get them to sub the 9mm barrel for a 10mm I might get the combo kit.

http://www.tnwfirearms.com/product-p/asrx-cplt-9445-xxxx-xxxx.htm

This is what came to mind for me. Glock magazines, AR carbine butt stocks.

They have a certain appeal.

? (AR15 10mm uppers is the question)

I have a 10.5" 10mm built by Ron Williams at RMW XTREME,  it is a DI gas gun that runs like a sewing machine . I use it on my MGI lower with glock 20 mags and also om my RMW XTREME grease gun lower with grease gun mags tweaked for the 10mm. It screams with 135gr loads and is a ton of fun with 180-200gr loads. The AR 10mm is a great gun, I always wanted an HK MP10 but the AR 10mm DI has filled that want.

I've been thinking about the Oly 10mm upper.
The only problem I see with that are the proprietary magazines.

Olympic sells blowback

You do start to get case blowby as your loads get really hot.

Other than a dirty chamber and cases no ill effects.

I've really pushed loads with a 180gr fmj out of a 16" barrel, the primers are near failure but still no issues with it being blowback. The cases do get trashed as the primer pockets stretch so bad they barely hold primers afterwards.

Ended up ordering the Olympic Arms upper.

TNW, Theuron and Mechtech all use blowback setups.