Hey!
As I understand it, the Affair comes in three sizes; mini, standard, and large. Do you definitely mean the large Affair?
I have two standard Affairs, and think the size is perfect! It looks well proportioned on me (I'm 5'7 and average build). I haven't seen the Large Affair in real life, but I think the proportions would look a little odd on me.
The standard Affair holds SO much stuff (much more than I was ever expecting) thanks to the sides which have studs on which you can keep closed, or pop over to expand the depth of the bag. The most that I would happily carry in my bag (without it looking overstuffed) is a purse (I carry a very small bifold, but you could fit a large on in), a 500 ml bottle of water, a couple of A5 notebooks (i.e. a diary and a notepad), pens, various pouches containing makeup, cards, keys, chapsticks etc, and my phone. I think you could stuff more in it too, but then it starts to distort the shape of the bag. Don't forget there is also a back pocket on the standard and Large sizes too, so there's extra space available, on top of the main compartment.
All in all, I highly recommend the standard size Affair. I have a couple of mini Macs (which I assume are more-or-less the same size as the mini Affair) and I don't tend to reach for them that much as although you can fit a lot in them, I really like to carry around a bottle of water with me.
Hope that helps! I actually have the Affair in pale grey. I really didn't like the colour at first (it looked really plasticky) but it has really grown on me. I conditioned and protected the leather, which took some of the sheen off it (which I prefer) and I love the colour now. As a bonus, the leather feels really durable and isn't prone to scratching.