I have really enjoyed all the QRP Labs kits I've built.  Just a couple weeks ago I put a 10m WSPR beacon on the air from here on Kauai using another Ultimate 3S kit and a low-pass-filter kit.  A successful result and quite economical.

I've used ProgRock2 devices several times as a crystal substitute, and I'd like to share my experiences:

-  The USB programming requires that you know how to use a terminal program to talk on a USB port.

- The output is a harmonic-rich square wave, so filtering may be necessary in some applications.  QRP Labs has very inexpensive low pass filter kits that may be helpful.

-  These are microcontroller/synthesizer modules and as such will spray significant radio noise.  When used in a transceiver or receiver you should be ready for some reception interference.  Shielding and filtering the lines into the ProgRock2 can help, but remember you are directly coupling the unit into your receiver.  If a birdie from the ProgRock2 happens to fall on a desired channel it might be a difficult problem.

-  If you are considering using a ProgRock2 in an FM transmitter application, you will need to make sure the rig uses phase modulation and not direct-FM.  Direct FM wants to frequency modulate the crystal oscillator, and if you use a ProgRock you can't do that.

I don't want to discourage people about the ProgRock2 - it is a very handy device and have successfully used them in projects.  But I have also been frustrated and given up on that approach.  It is important to realize the reality of the situation and manage one's expectations.