One thing about the Deck is that it uses *linear* mechanical switches, and some people don't like that. I've seen it compared unfavorably to the electric capacitance keys of the HHKB Pro, for example. Also, the Deck is 1-1/2" high, so you need to make sure you adjust your keyboard tray accordingly. I've been tempted to get one, but I think I'll save my money to get a second HHKB Pro 2 instead (for backup and to take to work).
I keep wanting to try the SMK85 with black Alps sliders that xsphat has (DSI never got back to me when I emailed them; maybe I'll try phoning them this week). xsphat says the typing feel is better than the HHKB Pro 2, but I find myself much preferring the key action of the HHKB Pro to the white Alps sliders of the Avant Stellar, so I'm curious if the SMK85 feels any different from the Avant Stellar.
Also, this Ask MetaFilter
thread is worth checking out about multiple keys being pressed. It turns out the Northgate/Avant Stellar boards are, well, stellar in this regard. Definitely the wrong form factor for the original poster, though. The Avant Stellar, at 20-1/2" wide, is just about the bulkiest keyboard around.