Just got back from my first trip using this SIM. It is my first ever SIM, to be honest, so I was not sure what to expect.
I've decided to give it my review because I took the advice of some on here, so thought it only fair I share my thoughts on the product too.
I must admit, I really could not be bothered to wait for the thing to self inflate, so I gave it 3 or 4 puffs and it was pretty much there. I know some will say about moisture getting in etc... but for me it did seem to take an absolute age to self inflate when I first opened it up before my trip and I'm too impatient for that.
The SIM was comfortable enough, for it's size, though being a little over 6ft I would have preferred it a little bit longer (my feet were off the end of it). I did try it out on my groundsheet before putting it on my bedchair and it held up well.
The one key thing and big positive for me was the extra warmth it gave me when it was on the bedchair. The amount of times I've woke up with a cold back despite having a memory foam, fleece lined bedchair, is unfathomable, but having the SIM in place literally eliminated this for me, and even if it turned out not to be so comfortable, I'd happily still have it in place for this layer of extra warmth.
Packdown is small
Extra Warmth (seemed like a lot of extra warmth for me, personally)
Wish it was slightly longer
Takes too long to inflate for me
All in all I am definitely happy I made the purchase and unless you struggle getting too hot anyway, I'd advise everyone to at least consider buying one, especially those that do Autumn/Winter campaigns. I've yet to use it in proper winter conditions, but I imagine it's going to be a game changer when I do get round to it.