If you'd do a search for Clam 5600 you're bound to find a plethora of posts on it, pros and cons alike.
Here's mine as I own the 5600, but cannot speak for the Shappell model you're looking at...
5600 Pros:
1. Roomy - 5x6 - MORE than comfy for two people plus gear (vex, 2htrs (buddy & a catalytic if needed), minnow bucket, rod holders hang on the spreader bars, misc jig boxes on the floor or in side pockets, and two fold up chairs to sit on. Still fairly decent w/ 3 people, just a bit cramped so to speak - but not horribly cramped IMO...
2. Mostly durable - I have only had 1 problem w/ mine and that is the hole cover slider/retention bar thingies broke. Had to call Clam up and order a few rivet screws. Pulled the old ones w/ a screwdriver and used a poprivet gun to put new ones in - no problem at all...
3. Keeps warm - I have been in a few other portables b/f and it seems like they are harder to heat w/ the same heaters I use? Maybe just me.... but mine seems extremely insulated and have no prob. using a buddy to get it to 65 or so in there on a cold day....
4. Plenty of windows
5. Fairly easy to set up (non-windy days)
Cons:
1. Its relatively heavy. Not too bad to pull w/o a sled and lots easier on a sled or some sort of pullable platform. If pulling w/ vehicle or ATV, disregard con #1.
2. It can be a PAIN in the butt to setup in the wind. Most cabin styles are tho... price you pay for a shanty w/ a floor I guess. If I could do it over and spend the money - I would get the Clam Voyager b/c of the flip-over style and weight isn't a concern for me.
3. Plastic floor can make creaky noises on the ice. If you're a paranoid nut about noise making... the plastic will make noise on the ice if on uneven surfaces or not insulated by snow.
I can't think of any other negative things about it - but I'm sure a few others from IS here will soon add to your reply. Don't hesitate to do some searching too! As I said - there is a TON of info on the 5600 here. All in all it is seriously a great shanty - so don't discount it just b/c of my 3 cons. But... if I had to do it over again, I might consider a flip-over. Just my $.02.
-WF.