Waterproof Cycling Backpack Recommendation?

Dear Readers,

Take pity on my poor husband who has not been on a bike in over a month(!) as he recovers from a big shoulder re-construction surgery.

His armchair cycling has got him shopping for a waterproof laptop-carrying backpack. I am particularly concerned with sight lines as he looks back, and he with it being a backpack because he really does need to keep his shoulders aligned for some time to come. He doesn't need a big bag, as he's actually carrying a very small netbook. It is too bad it doesn't have a solid-state drive.

He's considering this Chrome and this Ortleib, but we're somewhat overwhelmed with all the options out there. A few friends have weighed in with suggestions, PAC Designs looks actually really cool but I understand the messenger-style is a deal breaker in the context of his surgery. Readers, are there any others we should consider? Any comments for or against the two backpacks in contention?

Thank you ever so much!
-Charlotte