You do have to lean
into the turn for maximum effectiveness. For most riding, I bend at the waist to do so, but I agree with those who have said it is not as effective. Slipping a "cheek" off the seat really lets you carve a corner, but it isn't that easy, at least with the stock seat. The stock seat is somewhat sticky, so I find I have to lift myself up to move over. This is not difficult in a long sweeper, or at the end of a straight, but in back to back curves it can be difficult to do quickly...and is quite tiring. One thing is for certain, whether bending or shifting body position, between leaning into the corner and having to actually turn the handlebars, instead of countersteering and leaning a bike into a turn, the Spyder will give you a workout if you ride hard.
-Scotty