The leather is very similar to the Slim Flex, soft with a slight pebbled surface.
As you can see it has a different pocket arrangement to the Slim model, but is also has a side opening expanding pocket which can take an iPhone or similar smart phone. I've not really used the other card pockets in the A5 yet, but they would take quite a few business cards or even a Field Notes note book
I happen to have a Moleskine notebook which I've added to it. I use the Flex for when I go to my French classes once a week with a notebook for my French vocabulary and the other one for general notes it works well. Also all the hand outs are on A4 paper, folded in half they tuck in to one of the pockets easily and it is also nice and compact too.
The leather Flex is also available in other colours as well now, see the Filofax site for details. I noticed that there is now blue, red and orange as well as black
Chrissie recently bought the natural leather cover which also looks very nice. Take a look at her review here.
I'm really pleased with these two, very adaptable, and I've been discovering other notebooks that will fit them as well, so I don't have the expense of having to order from Filofax and paying the shipping each time.
I didn't think I would be able to adapt to using a notebook, but dedicating a book to a particular task does seem to work for me.