There were some K1 Challengers for sale in Makro a couple of months ago for around £50. Some chap was paddling about near my boat in his and told me and let me have a go. Makro is a trade only store... but I since saw the same boats for sale on the internet for around £60.
First thing that impressed me was how it was so stable I was able to get in from the stone jetty which was about 2 feet above it - not really doable in an ordinary kayak.
Next it had excellent handling - the most important thing and something I didn't expect from an inflatable, especially such a cheap one.
It was quite comfortable, although I was only in it for ten mins.. so would need a longer run to really tell you about that. It appeared to have adequate back support for someone not too tall (I'm 5'5") and was also apparently adjustable.
If I remember rightly it packed away in a bag about 2x1x1foot - including the paddle which was in three sections.
It wasn't bright garish colours for frightening away all wildlife within a 3 mile radius.... but then unlikely to be spotted by a helicopter when floating lost in the english channel either - so it depends what you want. It was mostly browney-grey.
It had a painter with strong fixing and grablines all round. It also came with a cargo-net fore. And I think some storage space aft.
It felt pretty sturdy PVC fabric.
The con was that the paddle supplied with it was not long enough, but as it came in three sections, it would be quite easy to replace the middle section with another pole cut to the desired length. The rubber around the hand grips were a bit of a design flaw in my mind as it hinders you doing a proper swivel-action... but this doesn't matter if you do the above replacement of the middle section.
I think it was excellent for slow rivers and canals. I would not take it e.g. on the River Severn on a spring tide.... however i'm going to buy one once I know how much money I'm getting with my redundancy package as it will be excellent as a little spare craft for pootling about in on the canal on which I live and dragging a zander-line behind me