This little tool is amazing. On receiving it, I was initially surprised at it's size - it's smaller than I was expecting (although I have no idea why I was expecting it to be bigger, it is exactly the right size and any larger would make it unusable). It's also packaged brilliantly, there is very little waste packaging and the plastic that it comes in is recyclable (and not one of those irritating types of packaging that you have to destroy with a pair of scissors / knife to get in to). The instructions you get with it (on the inside of the folded backing card) are simple and easy to understand. Please note that all you are buying here is the tool - if you don't have any chain cleaning fluid, get some.
It took me a little while to get used to using it - I found that on the first couple of attempts I wan't holding it in quite the right position, and as such kept causing the chain to slip from the front cog. Lead to mucky fingers while refitting the chain.
Once I got into the swing of things though, wow. This product is incredibly easy to use, and will clean your chain in no time at all. If you've got a particularly mucky chain (like I did) you'll want to change the cleaning fluid a few times for that brand new chain look.
I have only one criticism of the tool, and that is that the bristles on the brushes may not be as secure as they could be - I found a couple of them sticking out of my chain after I was done. It could also be that this is just a "first use" issue, and I won't have to worry about it next time. Either way, I'd only consider it about third of a star deduction, hence the five star review.
Cheap, easy to use, and highly effective. I'd recommend this tool to anyone looking to get a nice clean chain in a hurry.