Generally for muddy conditions you'll need a longish stud in a wide open pattern so they do not clog and generate the most grip. Will also be good on rock, ice and snow etc but obviously a compromise on road. That said the long sticky rubber on an Inov-8 mudclaw does have a cushioning effect, and I don't find them to bad on short sections of road.
The Inov-8 terrafly would be no good IMO - no real studs so will be like ice skating in the mud. Better off going for the mudclaw (300 out soon or the 270/333)if you want real grip. Some of the roclites would be ok (e.g. 295's) and as they are the 3 arrow shock zone, would be probably better on the road. Flyrocs and terroc are also worth a look.
Not sure what you run in at the moment, but although the Inov-8s are mimimal, the're not full on bare foot. The roclites still have a 9mm heel to toe differential so transitioning is not so much of an issue.
I'd also check out the mighty Mizuno Wave Harrier.
Edited: 20/08/2012 at 14:35