cammas: you are a good man
I took my little man (nearly 2) for a spin on the wee-rider and he loved it (as evidenced below).
He much prefers the wee-rider to the trailer. He can see all the action and (unhelpfully) grab both the handle bars and the breaks as desired. Luckily he is not strong enough to actually depress the breaks all the way - just enough to make the uphills a little harder.
The wee-rider is not the best designed contraption. It is a pain to attach to your bike and take off. The screws in particular are poorly located so that it is difficult to use your multi-tool (they are too fat to do a full revolution without hitting the side of the bar).
Also as I use a women's frame there is not a lot of space on the top tube. The child's seat is rammed up against my bike seat so that there is space for the forks to turn (which is why my little man can reach my handle bars). This makes going on single track a little tricky as I don't have enough space to get out of my seat to pedal. I have an extra small bike!
Overall it is better riding single track with the wee-rider than the trailer. Alex has a limit of 4km on the wee-rider (before he gets bored and wants down), but probably more in the trailer (although this is probably because I can't see him and too busy enjoying my ride).