As cnnashman suggests, the Outback lacks a flat deck to stand on; the Revo does have a flat deck, but foot space is limited and without Sidekicks, is not a sufficiently stable standing platform for most fishermen. I haven't tried Sidekicks, but would agree with augaug that they should be a great asset in this circumstance.
cnnashman wrote:
I suggested to Hobie that any future kayak models hopefully will have a much flatter floor, the only model they have thats excellent for stand up fishing is the pro angler.
They must have been listening because the 2011 Oasis does incorporate good stability and a flat deck. While not as spacious as the Pro Angler, it actually offers a great alternative in many situations. Here you can see the cockpit deck space:

With the advantage of being able to carry a second passenger, the added weight can make a more stable platform than the PA IMO. Dual steering handles allow your partner full control of the boat while you're fishing.

There is a learning curve to standing comfortably on these light boats as they can slip out from under your feet regardless of stability. To that end, you can use a "steady stick" (broom handle inserted in the sail mast holder) to grab if necessary or assist in shifting position:

A lot of users fail to consider tandems for solo use, but other than the heavier weight, they really offer no disadvantage at all and some obvious advantages of capacity, spaciousness and the ability to bring a partner if desired. They also have the unique ability to accommodate the evolve motor in one drivewell, pedals in the other drivewell AND the superior power-off steering of the Hobie rudder! Still much lighter than the PA, they retain excellent maneuverability.
A lot of your choice would depend on how dedicated you are to stand-up fly fishing. If that's your main activity the PA or '11 Oasis might be your best choices.
