Wow had never heard the term Mechless before....
Anyways we have been using the cheap Clarion that came out a few years back. Pairing 2 webOS devices, no problems (obviously only one active connection at a time). I don't know how many devices it will keep in memory but I have yet to delete one. 2 centros, 2 Pres, 2 Veers, and a Pre2. Maybe it has just been auto deleting when I add new devices.
For a cheapo deck, it is pretty clean looking and has held up well with 3+ years of use. Not the cleanest looking deck we own, but the streaming has been great. I also like that the SD slot is in the back of the faceplate so no slot in the front of the faceplate for that, also Aux input comes out the back of the deck which I prefer.
This deck is in the "daily driver" so I don't have much audiophile information on it (no amps or subs in this car). It pushes the factory speakers as nice as the stock Kenwood that the car came with (I have never been a fan of Kenwood).
The current version is sub $150 US, and looks cleaner than the one we have from the first generation of their first mechless design.