jstack6:
If you have the 12k for the EDrive mod, knock yourself out. Not to mention the $$ for their warranty.

Once broken in, the 06 HCH will get the FE of an older HCH +5% (58-63 while driven smart)

EV Mode is possible with the 06 HCH (100MPG on the instantaneous). Here's NASAgineer's directions:
1) Take your foot off the gas (coast) and wait for the instant MPG gauge to max out at 100MPG. At this point the valves are sealed and no gas is flowing.

2) GENTLY apply pressure to the accelerator until you see one or 2 bars of assist showing. If you do it gently enough, you can get anywhere from 1-3 bars of assist (3 is my record so far) with the instant MPG still pegged at 100MPG.