My favourite theme to date has to be Aerials V2 by Xavier, with a selection of blue, green and violet to choose from. I personally have the blue variant on my E71 and a few particular features I love are the way the loading bar, when transferring data or refreshing feeds, swings from side to side in such an exquisite manner.
Xavier has been my favourite source for S60 3rd Edition themes for some time now. His work is very thorough and the themes do not compromise any part of the interface as many others still continue to do. Fear – Is their latest theme and features the Full SVG Touch Icon Pack including over 400 3rd party application icons. There are six version packs included in the download for every S60v3 FP1 and FP2 device. You can download the file here.