Not bad for the price, the sides do tend to bow out if you put a little too much paper in them, if that happens you have to scrape off paper from the bottom and sides before you make a new brick.
People seem to have trouble squeezing the bricks down, I've never had too much trouble, I do make sure the paper is well soaked though, the method I use is below.
I rip the paper up in to around 25mm strips, put them in a large bucket, top up with water, mash around a bit, after an hour or so I give them a whirl with a mixer attached to a drill, the kind for mixing paint etc, this has two purposes, 1- to get the paper thoroughly wet and 2- to mash the paper up further, I mix it up two or three times a day over the next couple of days, the result is papier mache which is loads in to the brick maker easily and squashes down easily.
I make the bricks in a large plastic tub I have, this confines the mess to that one tub and residue water with fine pieces of paper in gets thrown on to the compost heap.
When I have a minute I'll make a video showing the process from start to finish.
Bricks take around three weeks to dry out completely this time of year, once dried they last about an hour, I'm not sure they give much heat out compared to say coal, but I suppose it is recycling in it's own way.
Is it worth doing, for the therapeutic value, Yes, for the money saving value, Not really.