Very easy process, just pass a few written and physical tests and your in! As far as the interview it is not bad at all. My interview lasted about one hour but all of the following up testing was time consuming.
Long process multi day and multi event. Respond to USA jobs vacancy announcement. Submit packet. Archduke interview with little to no led time. Interview was pretty easy. Oral interview then on the spot written (in ink) responses to questions. Final determination is made on the condition of a clearance and a drug test.
I applied through a recruiter. The process took 4 weeks. I interviewed at US Army (Ludington, MI) in Nov 2011
Interview
Recruiter reviewed requirements
Walk In - face to face
written testing - basic skills and math
Medical testing - to see your physical health level
background - to be sure you have no criminal charges
agility testing - physical fitness test