OK, so... I was impatient and went ahead & bought an HP Stream Mini Desktop to use as an HTPC. They were selling out on HP's web store REALLY quickly. Combined with a Flirc Universal IR receiver and a WDTV Live remote, it was the perfect replacement for a WDTV Live. The main draw for me setting up an HTPC over the WDTV Live or a Plex app for something like Roku was to eliminate the need for transcoding over my local network. WDTV Live plays every format I've thrown at it perfectly (with the exception of WMV), but the GUI can be glitchy and is pretty clunky in its presentation. There's no real way to keep track of what you've watched other than the Media Library feature which is cumbersome at best and downright ugly at worst & the presentation is a basic browser of files/folders.
I'm using the HP Stream to run Plex right now & it runs it beautifully. With Flirc I was able to keep the WDTV Live remote which I was already used to and it's perfect for Plex. Performance & responsiveness is fantastic and the unit is basically silent unless you are standing a few feet away from it. If the HP Stream Mini Desktop can be had for less than $180, I'd hop on a drop if you're in the market for an inexpensive HTPC.