By nasty drivetrain, I mean it's most likely worn out. There's a persistent squeal from the cranks while pedalling, not sure if that's the chain or the BB. I can't seem to get the rear derailleur adjusted so that it shifts right (though that's probably more an issue with cable than the derailleur. I also realized that my pannier may have been interfering with the derailleur). It's the original chain, which I have personnally never lubed and I think it's only been to a bike shop once in 15 years. The bike started out as my college transportation, spent a LOT of time in the garage after college, and got briefly revived when I got back into cycling. I quickly borrowed then bought road bikes. So, it's pretty neglected.
As far as looking for justification for a new bike, I am actually sensing that the suspension that sounded so good to me yesterday as I was being pummelled, probably is not going to be quite as satisfying. So, I might instead try fixing up the Rockhopper for now and see what kind of improvement that will make. (I just spent a ridiculous amount of money on my road bike a couple years ago, so I'm not sure I'd be able to sell the idea of another new bike anyway!)
Thanks for all the advice!