Yeah, my research and specialty is extratropical transition. We know that a change in the energetics of the two types of storms must occur during transition -- hurricanes draw energy and moisture from the ocean's surface, while midlatitude systems draw their energy moreso from dynamical processes -- but part of what we don't know about the whole thing is how this all occurs, how the storm itself impacts the environment, and so on. We're just starting to crack the iceberg on all of those topics...I expect we'll know a lot more within 10 years.

There's a new climatology that some forecasters at the Ocean Prediction Center did on HF-extratropical storms; they presented this work in Washington D.C. last week. You can read more about it here, including being able to listen to/watch the presentation as it was given: http://ams.confex.com/ams/WAFNWP34BC/techprogram/paper_94332.htm

Regarding the whole energetics issue and such....there is some research on both types, but unfortunately most of it is in archives that are accessible only to the educational community or for a small fee. You can do a search at http://ams.allenpress.com through most of the meteorological journals to see if there is anything that piques your interest -- maybe the library even has a subscription to the service -- and go from there. Sometimes a search for a particular article will come up with a free article somewhere.

The cool thing is that the midlatitude storms get a lot of their energy from conversions of potential energy into kinetic energy (with a bunch of transfers between small, medium, and large scales complicating matters). This occurs largely because of the vertical shear of the wind. I'd have to refresh my memory about everything, but it is one big cycle...potential to kinetic back to potential energy from birth to maturity to occlusion and death. I'll try to remind myself to look over the stuff again tomorrow and see what else I can add; if you don't hear back from me by Friday here, drop me a PM and we'll go from there.