I have a Colt with a .22 conversion kit. My dad got the pistol in a trade years ago with the "Colt Conversion Unit .22 Long Rifle" installed (I don't have any other barrel or slide for the gun). It has a steel slide, and the chamber is in two parts that slide into each other (tough to describe). I think I read somewhere that this was designed to increase felt recoil. It does seem to kick more than other .22s, thought not a lot.
Anyway, it works great. I did have the split chamber get stuck together a few years ago (it got some lead fouling and locked up). I had a tough time getting it apart. But that was the only problem, and that was after years of shooting a lot of cheap lead ammo with little cleaning. I think its a great setup for someone who has a .45.