Ukando has a skin that i use, the blue 1, but overall is Second Life official viewer with:
A quick tools button that allows to cycle and change windlight settings, increase or decrease draw distance, increase or decrease lod.
A world map that can be sized and changed to show it fully without the menus.
A draw distance slider by itself.
Rlv (that i dont use and usb works perfectly without rlv activated btw).
Area search finder.
A better camera position.
A worn tab on inventory.
And other improvements i cant remember but very useful without making it a huge resource viewer like firestorm.
For those that can not adapt to the v3 style interface, there is a obvious choice that i don't see mentioned here.
(i do refuse to use those old style interface anymore, it took me a week to dapt long time a go and i, for once, do agree that ll did a good job with the v3).
Cool vl viewer is the only tpv that is updated on a weekly basis and still uses that old interface.