If you ask me, Transom does some of the best digital audio recorder reviews around. You know, not including my own.
While Transom doesn't appear to have gotten their hands on a Sony PCM-D50 yet, they did recently post a review of the much anticipated Marantz PMD620. And while it looks like an excellent recorder in terms of build and sound quality, there are a couple of drawbacks, not the least of which is that there's an annoying latency issue when monitoring recordings with headphones. In other words, you'll hear the recorded sound echo back to you a split second after it's recorded. That means you'll hear each sound twice unless you have amazing headphones that prevent you from hearing any sound from the outside world.
I've updated my PMD620 review roundup to include some information from Transom's review, but I highly recommend checking out the full review.
Transom has also updated their incredibly useful portable digital audio recorder comparison chart to include the PMS620. You can also get an overview of other popular recordings like the Marantz PMD660, Zoom H2, Zoom H4, Edirol R-09, M-Audio MicroTrack, Tascam HD-P2, and Sound Devices 722.