I don't have much experience with the W4S, aside from having heard it at shows. I always thought it sounded great in those venues, but couldn't make a fair comparison. But, since the thread started, I picked up a PWD Mk II and PWT, and it's pretty safe to say that my digital needs for the next few years are taken care of. I've been extremely happy with the units.
I'd spent a bit of time in the PS Audio room at RMAF after the PWD/PWT debuted and had been impressed with it then. The fact that they offered customers who had purchased the original unit a clear upgrade path reinforced my decision that it was the right way for me to go. As of now, I am just using the PWT with the bulkier HDMI cable from Blue Jeans Cable. Perhaps down the road, I'll check out the Harmonic Technology Magic cable, but for now I have no complaints. I've also been using various laptops to stream and play back music files, and again, it sounds great. Whatever they are doing in terms of the Digital Lens, does seem to work to minimize differences in transports.
Down the road, I'll check out the Bridge and Silent Server, but I'm waiting to see how that plays out, in terms of their software eLyric and its development. I'm fine with Decibel, Foobar2k, and Rhythmbox for now, on their respective OS platforms. It will be nice to simplify down to one program for my stereo, but it seems to be a work in progress, according to the PS Audio forum reports. I feel fairly confident that they'll arrive at a nicely integrated digital front end solution, but I'm still going to wait a bit before jumping on it. I have most of my files in FLAC and don't have a strong desire to go the Apple music server route. I have high hopes for the Silent Server, but will wait until it's out for a while before getting that and the bridge. I may also look into the music servers sold by Sonore, which use Linux. We'll see.
If you haven't seen it, this review of the Mk II is also worthwhile reading for someone interested in the unit:
http://www.hifi-advice.com/PWD-MKII-review.html