I do not own a Krampus but have the 29+ wheelset ie the SURLY Rabbit Hole 29 x 50mm rims and Knard 3" tyres, called a KramPug
KramPug NB Law 016 by coastkid71, on Flickr
Can only comment on the wheels but my mate has a Krampus and its a hoot!
A bike that you could make full suspension bikes look very silly with at Trail Centres..
The Knards are indeed useless in mud, being a dry tyre, but not to worry as the SURLY Dirt Wizard 29 x 3" get released in Autumn
And look the biz.
Having ridden over 10,000 miles now on Fatbikes in nearly 6 years i have watched a lot of increased interest here in the UK on them.
However here in the UK there has not been as much interest in the 29+ of the Krampus as fatbikes, and there should be more,
Some things i have found with Fatbikes riding them everywhere are;
They are not replacements for MTB`s, but something differant,
They have uncontrolable rebound from the 4" (worse with 5") tyres at high speed - try riding one flat out doen Caddon Bank at Innerliethen.
They weigh more yet it is not really noticable until riding long climbs..
The 29+ wheels as the Krampus has started is a differnt sort of fatbike, i still term 29+ as a fatbike as you can run the tyre pressures at half of a regular 29er, 15psi instead of 30 psi.
My first Karate Monkey had Kris Holm 47mm rims with 2.55 WTB tyres, it was more comfortable and got more grip out the tyres climbing. nearly a half way house, it was close to what i was wanting.
The Knards though are faster rolling with less rebound than a regular 4" fatbike, no matter what weigh a fatbike is, or its type of tyres. Also there is no weird squirmy steering with the 29+, it just rides like a 29er but more comfortable and more grip.
3" is indeed half way between a 29er and a Fatbike (thats obvious!)
And way more fun and faster and more comfortable than both fatbike and 29ers. both of course are better at other things, only you can decide if it would be ideal for where you live and what you like to ride, i know i would have one in the gang, but the ability to offset the Rabbit Holes means i can have 2 in 1 bikes with the Pugsley
Hope this helps