first, there's no such thing as a "Freeview specific" aerial. The logo being added to otherwise unchanged products is just a quick way of making money.
The only thing to keep in mind is that in some parts the UK, some of the new Freeview frquencies are on very different frequencies to those used be analogue in the past. Its common to find that in many area's in the past, an aerial designed to pick up just a few frequencies was used, and these are simply blind to some of the new frequencies. The same thing was true by the way in some parts the UK with the launch of analogue Ch5 some years ago. You can buy (and always have been able to) aerials which work with all UK tv frequencies, and these are called Wideband (or type "W").
You have to keep in mind also that Freeview signals are a lot weaker than analogue at the moment, so where a small aerial works for analogue, it may not be enough to pick up Freeview, or some of the channels could be missing, or the pictures and sound might breakup a lot. Hence the reason why a lot of people need a bigger aerial than they did for analogue. As a basic rule, unless you have a clear view of the transmitter, a small indoor aerial wont work very well - if at all.
Last but not least, while analogue is broadcast by over 1,000 transmitters around the UK - Freeview is only broadcast from 80 of them at the moment. So for some people, they not only need a new, larger aerial, but to get Freeview it must point to a different (more distant) transmitter compared with the one they used for analogue.
Dave