Use Delta4 myself, as I'm not a fan of /viewport, and want something that has everything at the touch of a button but not overcrowding the screen.
With the horizontal spellbar option it's the best hybrid UI out there imo, and looks fantastic as well.
Only problems are:
Resolution can be hard to handle if your comp doesn't do 1152 x 864 or isn't big enough for 1280 x 1024 (although I've managed to force it to do 1152 somehow, will see if the graphics patch screws it)
Chat windows are a little small, but this can be sorted by getting fontsize / titlebar / bordersize altered to your satisfaction, or putting invisible text windows along the sides of the screen.
Delta4