However it goes beyond the standard HandBrake GUI in some areas. I've been able to call directly into the HandBrake core libraries, rather than wrap the CLI as the current Windows client does. The result is I get instant static previews of the source material, just like in the Mac version. The preview instantly reflects changes in resolution, pixel aspect ratio and cropping. Other advantages include the ability to pause and resume an encode and the removal of those pesky console window popups at the start of every job.

Beyond the tighter integration to the core libraries, I've overhauled the entire UI, including the workflow and preset system.

Feature List
Multi-threaded
MP4, MKV containers
H.264, MPEG-4, Theora video
AAC, MP3, Vorbis, AC3 audio encoding and AC3/DTS passthrough
Target bitrate, size or quality for video
2-pass encoding
Multi-angle support
Decomb, detelecine, deinterlace filters
Batch encoding
Instant source previews
Creates small encoded preview clips
Pause, resume encoding

Note: You'll need .NET Framework 4 (only the Client Profile is neccessary).

2.0
Added pickers! Pickers let you automatically choose titles, audio, subtitles and destination, as well as automatically queue or start encodes when a source is loaded. While encoding presets customize how a file is encoded, pickers control what is included in the file and where it goes. Let me know if there's anything else you'd like to see added to the Picker window.
Added a collapsible left panel to the Encoding Preset window, to switch presets quickly.
Changed window placement to open new windows dynamically in open areas rather than in preset locations.