It's perfectly doable to create good sample based tracks in Reason. But you couldn't finish and master something of the standard of a Prodigy track on that alone.
I once saw Liam walking along the street of Sarm studios around the time that 'Always outnumbered never outgunned' must have been in production: http://www.sarmstudios.com/ - I assume he came out of there. It's a touch more advanced setup than Reason ;) Although if I had to guess which album he made on Reason I reckon it's that one.
I doubt the latest album 'Invaders Must Die' was done on Reason alone because of the quality of the synths used. Although again he could have just programmed the rough idea on Reason and then used the midi-notes to drive high-end synth.
All of the electronic artists that are big in Aus right now do. Had drinks with a whole heaps of em at Bigsound a few weeks back and chatted to a few of them, all really nice people.
I know I've done stuff just point and click on the train home from work in both ableton live and Reason.
It's not quite as fluid as having a real keyboard (or other instruments around), but it is completely doable.