i have the original mutsy travel system rather than the new lightweight chassis version (bought middle of last year and still available in the shops so when i say original i don't mean really old!) but i do have the additional swivel wheels, so i think the only difference is the weight (though don't know for certain).
i was really pleased with the system. the seating unit is really comfortable, with lots of recline and depth positions and nicely padded. it also has a padded front bar, which meant that there was no danger of an over-excited baby hurting herself if she leant too far forward too quickly. lots of folk commented on it as it stood out amongst all the quinnys and bugaboos (not that that is a reason to buy it). the big bouncy wheels also make the ride fairly shock proof for the baby. i'm also told it's pretty good for 'off-roading' though i certainly never tried this option out.....
plus one of the mutsy car seats lies completely flat and fits onto the chassis, which sort of makes it into a pram. because of problems with delivery (i ordered mine quite close to the birth of my baby and it took months to arrive) we used the car seat/chassis option far more than the seat and it worked a treat.
sadly i didn't get to use mine very much due to it's late arrival and i'm now having to get rid of it as i'm expecting my 2nd baby and have fallen in love with the phil & ted's (i like the little drop down shelf for the newborn!), but i'd definitely recommend the mutsy as a really good buy for comfort for your baby. the only possible negative is that it is quite big, but i don't know how it compares to other buggies in this respect and unlike others, you can collapse it with the seat unit still attached, which is pretty useful. also the wheels (on mine at least, but can't imagine the lightweight version is too different) come off just by pushing a button in the middle, which takes seconds.
hope this helps.