Dazzle (the Linden Lab project for updating the appearance of the Second Life viewer, and not the fashion brand) has made it into a separate First Look preview viewer, rather than being a manual download and install.
Linden Lab's Dazzle project serves two purposes; one being a graphical overhaul of the Second Life user-interface, and the other being to further develop the interfaces that allow the user-interface to be reworked, reskinned and customized.
The First Look Dazzle viewer appears to be based on the regular release candidates, and is separate from and parallel to Windlight. So, no Windlight rendering improvements here.
The First Look browser is a beta-test browser that runs against the main (Agni) grid. If it eats your inventory, your files and your dog, that's at your own risk. The viewer is available from the First Look downloads page right now. We recommend the use of a download manager to save download time - it can cut 90% or more off the overall download time for many users.
Personally we found the squarer shapes for buttons and progress bars felt like a bit of a step backwards from the canonical, more-rounded UI. Contrast has improved from earlier previews, though the two-tone coloring of the toolbar buttons all the buttons seems to make them harder to look at. We think it's supposed to give more of a pseudo 3D appearance to the button images, only ... well, it doesn't seem to.
Nevertheless, this isn't about what we think, it's about what you think. Tried out Dazzle? Tell us what you think of it.