I use them for almost everything they can be used for.
I currently have seven with R820T tuners and three with E4000 tuners.
Four of the R820T's are connected to a USB 3.0 powered hub and ready to go instantly.
I use them for antenna testing, preamp evaluation, checking unknown signals, digital decoding, watching parts of the RF spectrum, downloading NOAA weather images, airplane tracking, SSTV, and I'm sure there's other things I forgot to mention.
I have SDR# installed in 14 separate folders.
Several of those folders are set up with VB Audio cable or VAC and configured and ready to go for all the digital stuff.
That way I don't have to keep changing the configurations.
I can swap from audio to digital modes instantly. OR copy digital modes and analog modes simultaneously.
All of the applications I use would take a lot of typing so I've attached a screen capture of the desktop on one of my computers.
You can click through to see the high resolution version.
Most of the applications I use are across the top of the desktop.
There also trunking decoders at the bottom right corner.
At this point, I don't know how I ever got along without them.
Rich
Desktop
And here's a comparison of four different ST2 antennas simultaneously receiving the same SatCom signals.
Each image is labeled with the direction the antenna is facing.