I just received my first ever Tom Bihn bag: a black and crimson Smart Alec with a size 4 crimson Monolith insert. I've only just begun to use the bag, but so far I'm quite pleased!
The one thing I've run into so far that does distress me is the lack of protection on the zippers on the Monolith. I cringe everytime my aluminum powerbook scrapes by them as I insert or remove it. I own a "SportFolio Sleeve" from Marware that I used in my old backpack explicitly to protect my laptop from its zippers. The nice thing about the sleeve is that its own zippers are lined with neoprene which extends out past the edge of the zippers, so the laptop never comes in contact with them when being inserted or removed from the sleeve.
I actually tried to continue using the sleeve and inserting it into the Monolith, but it doesn't fit. I even considered removing the padding from the Monolith and relying just on the sleeve's padding, but it appears that the Monolith's padding is sewn in. I'm not sure I'd end up going for that anyway, since the sleeve wasn't really meant to provide padding.
Anyway, my suggestion for the future would be to consider some sort of extended lining or other protection on the Monolith so that the laptop will never come into contact with the zippers. I haven't come up with a good solution yet for my own situation, but I'll figure it out. Maybe I'll try sewing on a neoprene liner if I'm feeling particularly ambitious.