Since the Hyda is apparently pretty popular in the mister-two community they've got some pretty good documentation for it available. I found this tuning guide very informative:

http://mrcontrols.com/installs/nemesis/tuning.htm

How does the nemesis differ from the Element?

The Element Hydra is electrically plumbed for the impreza, otherwise it is the same hardware. That site also has the Nemesis 2.1 software for download. I've been playing with it for awhile. You can learn alot just by tinkering with the base maps.

The real difference with the Element Hydra is the "mapping" and "programming" that Phil Grabow has done for the WRX and STI. He's tuned and tested his maps under multiple temperature, driving, racing, and loading conditions. Doing it yourself would be a major undertaking. Phil has a lot more experience than most of us, and he has the tools and low level code access from Quantum to tweak everything for the turbocharged imprezas. He's worked out the idle, cold temp compensation, a/c activation, shift transition, and longterm load conditions--to name a few. Plus, he's squeezed a bunch more power and improved the throttle response over the base maps in the stock ECU.

The Element Hydra will give you enough rope to hang yourself with, or the pre-package maps will give you confidence that nothing will go wrong (a la EcuTek and AccessPort). Unlike UTEC it is not piggy backing on the stock ECU signal so there is more versatility and no worries about fighting the ECU's own learning algorithms. Also being MAP based instead of MAF based it's easier to run larger turbos without maxing out the MAF sensor. Air intakes and turbo inlets can be as larger as you need since there is no MAF diameter to constrain air flow to a set diameter with laminar flow. Atmospheric BOVs can be used without temporary rich fueling because the MAP sensor will offset the loss of air out of the valve.

Thanks Darshu.