Really, I haven't looked really deep into it yet. What I was going to do was talk to a rep over the phone about the system as well as who I can bring it to to install it etc etc. AEMpower.com has a number listed strictly for the EMS I think.
Now here's a tip, DON'T buy from the AEM site and here's why:
http://www.sfxperformance.com/parts/AEM301900U.htm
See the difference
Now one of the people that is helping build my turbo knows quite a lot about the EMS and tuning, so I have help there.
I also have to agree with you, I want full management of my maps, switch maps on the fly, have a rev limit to take off at, switch from an all out racing turbo map to stock, everything! But I never looked into the Greddy E-Manage so I'm not sure what that has in comparison to this EMS.
Edit: Also I think you'll need a custom harness made wherever you get it installed at