I just posted an update to the cups extension and would be grateful for some testing feedback.
I only have access to a couple of hp officejet printers which need hplip to print and a lexmark z600 which appears to be too old to work with tc-3.x, so if anybody has a usb printer to test, that would be great.
There have been a lot of problems with cups-1.4.x and usb printers - this version of the extension has been compiled using the cups internal usb backend (as opposed to the libusb backend).
In my case at least, this version of cups-1.4.x does not seem to require the usblp module to be blacklisted - this statement is based on the observation that I get this without blacklisting usblp:
direct usb://HP/OfficeJet%20K80?serial=ES0911401VOH "HP OfficeJet K80" "HP OfficeJet K80" "MFG:Hewlett-Packard;
MDL:OfficeJet K80;CMD:MLC,PCL,PML;CLASS:PRINTER;DESCRIPTION:Hewlett-Packard OfficeJet K Series;
..but I get nothing if the usblp module is blacklisted.