I used to have the same opinion, until I bought one.
As standard it wasn't spectacular, but with the addition of a Maccari kit the rifle was somewhat improved, with a power hovering around 7.5ft.lbs. It is surprising how effective this is on an FT course. On the zeroing range it knocks down and resets 55yard targets no problem and the groups at long range are very good.
I now have several FWB300's, the best one to date is my Universal, re-sprung with a POK spring this one gives a consistent 695fps +/-5fps for a steady 9ft.lbs with JSB's (the rifle still works within its design capability and doesn't use the entirety of the recoil sledge track). In fact I am confident enough in this one to start using it for FT in the SWEFTA league shoots next year.
http://www.airrifle.co.za/picture.ph...pictureid=3888
BTW - Germany and Hungary have classes in FT for low powered rifles and they seem to shoot OK with them.....