The space that I have to work with is pretty limited and it needs to also work as a pass through (the stairs to the finished attic originate in my new office.) The Tread Desk (www.treaddesk.com
) "Tread" at 58"x24" is the smallest motorized treadmill that I've found. The fact that it's supposedly designed for long term walking is also a plus. It's just that I haven't seen anyone's review on this except for the owner of the company (and I'm sure he'd admit that he's not unbiased.)
Not having arms shouldn't be a problem for me as I'm planning for a new desk in the new office anyway so I'll just go with a tallish standing desk.