I used to have a mountain bike, and was forcing myself to ride it. I don't remember the brand, but it wasn't purchased at a big box store. Anyhow, I finally went to a bike shop and asked them why I hated that thing. He had me sit on it, and immediately said it was the wrong size. He fit me to a Trek 7100. I was still skeptical, so he suggested that I ride it around the parking lot. Holy crap that thing was comfy! I put some more aggressive tires on it because it does occasionally see a non-paved trail. The rolling resistance was quite noticeable.
Now, 7 years later, it's starting to show its age. I looked at new bikes, but disc brakes are really the only upgrade, and I don't think $600 is worth it for discs. I asked the shop about a tune up last weekend, and was quoted $250. I decided to do the work myself. I put on a new set of touring tires. Less aggressive tread and less rolling resistance, but I think they will handle the small amount of off pavement riding that I do. I don't think the cables are worn out, I will lube them. New brake pads are coming.
It is not a trail carving bike, I've done a few 50 mile days, but it's not really a road bike either. It is a great all around bike. It's not so flashy that I am afraid to leave it locked to a pole downtown, it's light enough to be easily tossed onto a car rack, clip the panniers on it and it is wonderful for running errands.