No, they aren't worth a 7h drive for MTB'ing - climbing/walking yes the but terrain really doesn't lend itself to memorable MTB routes. Scenery is fantastic, but it'll be mostly flat on the routes above.

Loads of memorable stuff en route though.  Hard to know where to begin really.

What's your itinerary like ?

I would head up the A9 to Dalwhinnie - then go left to Fort William stopping off at:

Laggan Wolf Trax - Meant to have quite a technical black trail.

At Fort William:

There's Nevis range - few threads on here a month ago about the new DH for XC'ers track. Probably up your street as it looks quick techy without needing full DH gear.

Obv. the Witches Trail as well.

For something a bit more dramatic in terms of scenary / remoteness on the way back - The Gaick Pass.

Will need to sort out return transport though on the last one - can be done with a train from Kingussie to Blair Atholl - but book in advance, or you can get stuck!