I got the previous Prima model from Bid/PriceDrop for £23 including P&P. The TSV is better because its lowest setting is 60deg, mine's is 70deg which is sightly too high for simmering, but I add a drop or two of oil to the water to prevent boiling over.
One reason the Prima is cheaper is that it does not have a ceramic surface, it's Crystallite, which is some sort of strong plastic. It marks more easily than ceramic, so be careful if using Le Creuset and suchlike.
A bonus with the TSV is the 3-hour timer, the 'old' one only does up to 1 hour. The timer is terrific for me as I am so forgetful.
I love my induction hob so much that I've just bought a full-size one to replace my gas hob - don't worry girls, it's secondhand and comes ready scratched and chipped, so I don't have to worry about spoiling a brand new glossy one.
I think the TSV is great.
clemenzina