I use the Matrox MX02 with max hardware with the accompanying matrox h264 codecs they include. Output is fantastic at all the HD res's (1080 30/i/p, 720 30/60/p), file sizes are small and most importantly, the conversions and transcodes are very quick with the hardware assist. They have conversion settings for compressor specifically for Youtube, Blu-ray, Iphone, Ipad.
If you can afford the unit, it is invaluable. It does a ton of things (HD monitoring, cross converting, capture, hardware assisted acceleration of effects in FCP/Avid/Matrox (in October update)) in addition to the great job it does with h264 compression.
More info here:http://www.matrox.com/video/en/produ...ily/mxo2_mini/
I don't work for Matrox, but I am a big fan of this unit.