I just had mine nitrided at MMI. Actually I had 2 barrels done. 1 was a Criterion 30" 7mm RM and the other was a 26" Savage 22-250. I put about 20 rounds through each to establish accuracy and velocity. Turn around time was less than a week. Cost was $60 per barrel + $20 return shipping and there is a $100 minimum. Accuracy was not affected in either direction best I can tell and I gained an average of 50 fps. The biggest benefit will be a longer barrel life, but obviously that will take a while to prove.

Here's this year's rifle.
Savage 7mm Rem Mag
30" Criterion bull barrel ... nitrided by MMI
RWS brake
Bolt knob from Midway installed by me
16x SS, EGW base, Burris Signature rings
Choate Tactical painted with stone texture paint
Matte Black DuraCoat
175 SMKs moving 3,100 fps

[img width=600 height=188]http://i66.photobucket.com/albums/h270/mscott_photos/7mmrm1.jpg[/img]