Just upgraded to SL and all was well until I tried to print something. SL showed no printers installed and failed to find my networked Canon MX860 (it did find an MX860 bonjour scanner but that didn't do me any good). SL has a built in MX860 driver but it was worthless for connecting to my networked MX860. When I tried pointing to the MX860 IP address it simply failed to identify the printer, maybe someone else knows how to get this working with the built in SL software and drivers, would be good to know. So after pulling hair out around this for a few hours here is what I ultimately did to fix it; 1. Make sure you are on the latest version of the Navigator software, ij network assistant software, etc. This is a pain because Canon doesn't have a single package that updates ALL of these, you have to do them one at a time AND REBOOT AFTER EACH which is a giant pain in the ass. 2. Download all of the Canon print drivers (there's a CUPS driver, a general print driver and a SCANNER driver, get all of them). 3. Click on the Canon ij Network Utility in the OS X menu bar and remove any existing printer and scanner references. 4. Install the SCANNER drivers. 5. Click on Canon IJ Network Utility and re-select and enable your scanner. Your scanner works now. Too bad your printer doesn't. 6. Mount the disc image for both of the printer driver packages by double clicking them. Drag each installer package to the desktop. CTRL-Click the package and choose "show package contents". Navigate into the package RESOURCE folder. 7. Delete the "Installation Check" file. 8. Install the drivers. Do this with both driver installation packages (I'm not sure if this is really necessary but I had some problems until both were installed). 9. Open up the system preferences -> Printers, right click in the printer area and choose "reset printing system". 10. Add your printer, it should now be showing up again and should be working. I curse how hard this was to fix. Canon should be ashamed of themselves for not being on the stick with an update that would have taken care of all this. Best of luck!