Got to agree with everyone above. I use our Passat wagon and Outback Sport for supporting our mountain biking/kayaking adventures. Although the idea of the Baja is strangely appealing, its practicality is kinda lacking.
To me, the advantage of having a pickup bed would be to avoid using a roof rack. Since the Baja's bed is so small, two mountain bikes fill it (and you need to use the extender) and even a short whitewater kayak won't fit. The passthrough into the back seat won't help much either, except maybe for kayak paddles - but who wants to drive with that thing open to the elements all the time?
Plus, any of these sports has both big stuff (bike/kayak) and tons of ancillary gear (helmets, packs, clothing...) You either need to put a roof pod on a Baja to hold this stuff (or pack it into dry bags) or put it in the backseat, losing cargo capacity.
Seems to make more sense to buy a closed wagon and a roof rack - capacity for four plus equipment, and all of the stuff goes on the roof (or, if you're lazy and travelling solo, you can put the bike/boat inside.) As for me, I'm torn between the 2.5XT and the 2005 Legacy turbo wagon - I think I'll wait....