I have a hybrid Yaris. So far no problems with it but I do take it to a Toyota dealer for servicing as I don't believe that the complexity of the hybrid system is understood by your average back street garage.

A couple of things I have noticed.
It is more efficient in summer. One reason is that the battery is more efficient at higher temperatures, another is that the heating system needs the petrol engine to run to warm you up.
The battery is recharged when running down hill but here in the Pennines it is quite common to have it fully charged long before you reach the bottom so you are "missing out" on some free energy.
I reckon to get 40-50 mpg in winter and 60-70 mpg in summer. A trip across North Wales gave me about 71 mpg until I hit the motorway on the way back. The ups and downs were the right frequency to keep the battery charging up to nearly full.
Motorway speeds do bring down the mpg but town driving is excellent as you are using electric a lot then.
One thing they don't mention is that there doesn't seem to be a way to jump start another vehicle from it.
I have to have a 4x4 as well living where I do for the winter snow and ice.
It is more affected by crosswinds on the motorway than my Yeti, which surprised me as it looks more aerodynamic, is quite heavy for its size and otherwise feels quite solid.
I am now quite used to it being an automatic, which it has to be for the hybrid system.

Robin