I've used the 746PRO on 6 meters once at a field day. I don't know much about the radio other than that. But I did purchase a used Kenwood TS-2000 today for $1100.00 I have read about the things this radio can do, and have seen people's YOUTUBE demos on the radios capability (search K7AGE on youtube)
One function the TS-2000 has is the telecommand II. I will be able to take a dual-band HT or Mobile, and control my TS-2000 via the RF on the HT/MOBILE and operate HF. So I can be outside in the yard, or down the street, or in the bathroom and work DX through my HT. Also with some specialized software (free download) I'll be able to control my TS-2000 via the internet, and by using a laptop, Ham Radio Deluxe, Skype, and winVNC I'll be able to control the TS-2000, and talk through it from my laptop anywhere in the world that I have broadband access. (K7AGE has a youtube video demonstrating this very feature)
It has the Satellite function built in for Doppler shift. You can add 1.2ghz option if you want to work that band on Satellite or other things hams are doing on there too. It has a packet TNC built in, and DX Cluster feature on-screen. I use a cluster but do it through my logging software but it is a neat aspect. Someone mentioned using the 746pro mobile, well the TS-2000 has a control head which is about the same size as their dual-band mobile control head, so you can mount the radio in the trunk and put the little mobile control head in the front. They come with all of the filters. You also have the option of buying an INRAD 8 pole crystal filter for ssb/cw and the comments made on that were something along the lines of the INRAD filter for the TS-2000 making it sound just like a collins S-LINE!