Don't know how long it's been since you've used the WDTV boxes but the ugrade to the Mochi interface on the newest Live and Live Hub is pretty intuitive and if you set up the media library from your network shares it's a pretty attractive way to scroll through your library. It'll autopopulate most metadata, thumbnails and backdrops.
Is it the best? That's subjective. The pricier Dune HD box supports some audio formats like True-HD that the WD boxes don't, but you could buy 3 WD Live boxes for the price of 1 Dune HD. I couldn't tell you how the interface compares, but my 7 year old figured out the WD in about 2.3 minutes and the WAF was pretty high for my Live Hub. The Boxee Box seemed pretty smooth, too, but didn't do anything I needed that the WD didn't do for less.
You may want to look into the Mede8er and Popcorn Hour boxes, too. Stay away from the Pivos boxes. They are a geeks dream but the interface is just awful.