My only experience with magtech .38 ammo is with their 158gr SJHP standard pressue loading. I have an 1924 S&W M&P w/ 5" barrel and I was looking for a standard pressue HP loading to shoot in it. Magtech claims 807fps...I chronoed it at ~700fps from the 5" barrel IIRC
I decided that I would stick to the old standby Remington 158gr LSWCHP +P in my M&P.
I load my KT sub2000 .40 with their 155gr JHP. Magtech claims 1205 fps, out of the 16" barrel in cracks 1400fps. I just picked up 4 boxes of magtech +P+ 115gr 9mm for my S&W 910 and SIG P226. When I get a chance to chrono it I will post the results.
All in all, I think magtech makes decent quality ammo for the $$$. If you can find it, Fiocchi also makes very high quality, reasonably priced ammo.