I have one on loan from my local dealer and have for about a week. Placing my order today after an entire week of testing it out. But I use a Zen MINI MKIII and it drastically improves it with exactly the same things LiquidSound said above.
When I listen for a few days with the Phoenix, and then remove it I notice a collapse in Soundstage, less bass, more grain and less refinement and air. When it goes back in, it's like an all new server. Refinement, smooth, wide soundstage, more holographic, etc. All the good things get better, and not by a tiny margin.
I also have the power supply on order for the Mini III and feel a Mini with Power Supply and Phoenix will be quite special. It already is with the re-clocker. My dealer says he has no idea if they are in stock, which tells me there may be a wait. I have been waiting on my Mini MKIII power supply for about 3 weeks now. The Mini III came in one week.
Anyway, the Phoenix makes a difference and a good one, with the Mini MKIII. IN fact I auditioned the Zenith III and prefer the sound of the Mini III with Reclocker over the Zenith III. It took me a week of audition to relieve I had to have the Phoenix. Again, when I took it out...I lost a lot of the magic. Cant explain it, but it works and I am not using crazy cables. I have one Audioqest Diamond USB and one Forest USB. The Phoenix ships with a power cable and USB cable. I tried the stock USB and it's just as good as my Forest. I do not feel I need to buy another Diamond and won't. Nor will I upgrade the power cable on the Phoenix. Its great as is.