This little thing is so, so much better than the specs sounds. These little beasts can fill a room the size of a small school sports hall while still being easily transportable.
The advantages are clear:
Transporting the gear to a gig on a train etc is easy, due to the size and weight being so limited. The speakers being passive makes them light enough to fit onto a mic stand comfortably, which again makes transport convenient.
They are also far, far more powerful than you'd expect for being 100W. I can't explain how good these are for their size, considering the price as well. The flexibility of the mixer as well is fantastic, with the inputs allowing everything necessary for small events.
Ease of setup. This wee rig is easy. So damn easy that anyone could set it up and work it, regardless of aptitude or training. The fader system also makes it much clearer what amplification is being used, and dropping it to zero in an emergency is easier.
Cons:
Lack of expandability. Being passive, the setup can't be enlarged to 4+ speakers, or a larger mixer. There are really no other down sides as far as I've been able to tell.
If you need a cheap, self contained rig that'll fill a small room and is easy to move, then this (with some extra cables etc) is the rig for you.