Hours of riding up for a few minutes of down? Hell yeah!
As for MacDhui, there are several very clear and distinct tracks up and down. I just can't get myself to be in any way concerned about the mountain when it's covered in walkers on muckle big tracks that they made by tramping up it. There's no reason to go off the tracks when on a mountain bike as much of it is either very loose or grassy, neither of which would appeal. Part of the fun is the "rideable or not" technical nature of the paths. It's a shame that the desire to keep the high places special doesn't extend to getting rid of the funicular or the spectacularly guff mountain top cafe on Cairngorm.
I suspect you either get it or don't when it comes to taking a bike into proper mountains. For me, the best days involve going high and if there is hike a bike, it's all part of the experience. The ride down is a bonus – it's the journey that counts.
I rode a big loop of Cairngorm, Ben MacDhui and Bynack Mor yesterday. One of the best days I've had on the bike in a long time. 24 miles – 9 hours – mostly riding with plenty of stops to soak up the scenery. Marvellous!
Cheers
Sanny