I'm just bumping this old thread that I started last year. I've recently bought myself a Giant Rapid 4 which whizzes along effortlessly. It's got road bike features and tyres but has flat handlebars and the gear shift is so quick and smooth. My old 100 quid MTB was such hard work that I never did the 8 mile journey to work in less than 1hr 5mins and it just got harder, tiring and tedious. On my test ride on the new Giant, I did just shy of 8 miles in approx 33 mins with junction stops, and that wasn't going flat-out, I was cruising and just having a comfortable ride using the middle chain ring gears.
Honestly, if anybody is struggling on a cheapo bike, just get yourself sorted with a road bike. The difference is incredible. I used to HATE the journey to work on my old bike, it seemed like a hard, unrewarding toil. I knew there had to be something wrong with that bike. I've rediscovered what I seemed to remember from my youth, that cycling is and should be enjoyable.
Strange thing now is the speed of this new bike - I'm actually scared of going too fast