I used to have a LoneWolf 9mm barrel for my G35. Ended up buying a G34 and selling the barrel, but not because it didn't work. As someone stated earlier, you can't use it in IPSC Production, and you probably wouldn't want to shoot a 9 in Standard. Can't use it for IDPA SSP either, or GSSF. So, if you just want it as a range gun, it will work fine.
The barrel just drops in, and you need to use a 9mm magazine. Empties get ejected pretty close to the gun, but I didn't have any FTF or stovepipes in the 200 or so rounds I ran through it. If you wanted to make a permanent conversion, you could just order a new 9mm ejector from Lonewolf. The barrel wall is thicker than normal, so you end up with a heavier barrel. Combined with the already heavier slide in the G35, and a tungsten guiderod, the gun barely moved in recoil. Too bad you can't use it in competition since it was a really sweet setup.