Relating to the rtl-sdr work that has been done, the E4000 tuner was the standard barer for a long time. However, Elonics has discontinued this part, and it's becoming difficult to find. The popularity, and scarcity, of this part has encouraged sellers to offer products claiming to be built with the E4000 and are not. Luckily, someone discovered the code for using the R820t tuner in the Linux V4Lin drivers. They ported this code into the rtl-sdr source maintained by osmocom.
I just finished porting their code into Cocoa Radio. Now, it's possible to use my software with both the E4000 and the R820t. On startup, Cocoa Radio will automatically detect which tuner you're using and perform the appropriate actions.
It did take a little while to finish this work, and there are several more tuners out there. If you are desperate for support of a specific tuner, you can donate a device for the cause and I'll try to support it. By the way, Softshell uses the same code for tuning as Cocoa Radio, if you recompile softshell, it should include this new code.