Linden Lab’s Windlight version of the Second Life Viewer will soon be available as the standard viewer. As Soft Linden on the Second Life Open Source Developers mailing lists just announced it will be part of the 1.19.1 release candidate of the Second Life viewer.
Windlight is a complete revamped graphics engine for the Second Life client which brings better and more flexible lighting, better skys and better water rendering (including refractions and mirroring as you can see in the snapshot above) to Second Life users. It’s also supposed to run with less minimum system requirements than the previous versions of the client.
Right now version 1.19.0 is close to being released and available as Release Candidate 4.