I like them a lot and now have more 4" pads than 6.5" 'ers.
So far, I have 6 of each pad, cut, polish and finish - but have only used the latter two. I usually bung a few more in the cart each time I buy things from here as I have not seen them for sale in the UK. The SFX pads seem well made and are holding up nicely.
The 4" finishing pad is great for AIO, CMW and EX-P etc. and I use it for the whole car as I can't be doing with swapping backing plates halfway through to change over to the larger pads. The PC seems to work more efficiently too, as there is less weight/mass to throw around I guess.
Other people prefer the larger pads, but its what works for you in the end. Apart from that, there is not much more to say about them.