The 04 and Alpha interiors are almost identical. The gear shifter is changed and relocated where the T case shifter is on the 04. They swapped the two.
The daily driving in the alpha is better for acceleration (night and day between the two) and there is a little less rocking at stops due to some updates. I recently took an Alpha for ride and noticed the difference between the 04 and the Alpha as soon as I pulled out of the lot.
THe alpha is still not a racecar, but was a definite improvment.
There are a few other upgrades you can read about @
http://www.lynchhummer.com/changes/h...ges.index.html
This link will give you detail about the updates.
The comment on the post above "the Alpha doesn't have as many tech's to work on the DMAX and Alison" is BS. The DMAX and Alison setup has been around a few years in Chevy/ GMC trucks. THe setup is a little different, but not by much. Most dealers are also chevy dealers and will be able to get parts wihtout issue. You have 5 HUMMER dealers in IL (two that are close to you) and will be able to work on your H1 either way. Each HUMMER dealer has to keep a certified H1 mechanic on staff (at least that's what I was told by my local dealer and Lynch HUMMER as well).
The price is the obvious difference. You can find 04's 70K to 85K with low miles or the Alpha is still up just over 100K to 115K for a low mile truck.
If I had a choice, I'd go with an Alpha. If you go with an 04, just make damn sure you know who owned thw truck. I had an 04 for a short time. PM me if you'd like more info in that experience.