AG,
Sorry I didn't see this thread sooner...threads move off the page much too quickly nowadays!
I think the Grand National courses make a delightful weekend...my wife and I have spent 3 such weekends there and enjoyed each one. The courses are not perfect by any means, but the value proposition, combined with the new hotel, make it a great destination for a reasonable golf vacation.
As for walking, the Lake course is a difficult slog. We hiked it once and found there to be too many long walks in between green and tees (think 9->10 and 16->17). The Links is fine to walk...there are still a few long hikes, but none that will put you behind pace, save 1->2.
IMO the Links is superior to the Lake; there is more variety in holes and strategy is more important. Shaping the ball on the Links is a definite advantage, while the Lake course emphasizes straight and long. The Lake's opening hole is weak; I just can't get over teeing off with a middle iron. Also, the par 4 holes require similar clubs into the greens. The back nine is quite nice but the long haul over the river hurt the flow.
Besides 1, 2, and 18, I am a big fan of the Links course. While some call the green contouring over the top, I think it makes you think off the tee, which can only be appreciated after a few rounds. Take the 7th hole. It appears boring from the map (no greenside bunkers if I remember correctly), but the spine in the back of that green makes you place the tee shot. 18 is too much like the closer at Bay Hill; with that downhill lie its just too difficult to hold the green. Another quirk is that the middle holes (8-11) are all short holes, but not necessarily good ones.
Next time be sure to play the Short Course...its the best one I've ever played. Its a great 2 hour walk around some really fun holes.
An ideal weekend itinerary is:
Sat - Walk Links morning, Ride Lake afternoon,
Sun - Walk Links morning, Walk Short afternoon once or twice, depending on time.