recommend your pannier for bike commuting

[CrazyLucky]

My cousin is really big into bike commuting.  I recently switched jobs and now have a commute that is short enough to try bike commuting.  He let me borrow his bike and I really did enjoy it.  I'm not as into it as he is, and I'm probably done until spring.  It was 34 when I left the house this morning and I'm a wimp.  Anyway, I'd like to put a pannier on my Christmas list.  I would like it to be waterproof, fit a laptop and lunch, and have some type of structure to protect the laptop.  Is there anything else I should look for?  My cousin recommended Banjo Brothers, but I couldn't find exactly what I wanted with them.  I appreciate recommendations or other input as to what I should be considering.  
Edit: I'd also like to to easily convert to a backpack or messenger bag.

[wawa]

do you already have a work bag you like? I think if i were starting a bike commute right now I'd consider something like the classic ortlieb backroller which is just one big ass extremely waterproof, bombproof black hole of a bag with the intention of dropping my normal work bag inside it. That way I can also stuff in any layers I wore in the morning that I don't need now in the afternoon, or stuff I want for the ride home, my work bag stays TOTALLY dry (not just dry on the inside, etc), I can toss in my change of shoes if I need one, I can probably get away wiht some light errand runnign on my way home and have room for THAT stuff too, etc.

But that's with my work's bike parking situation, which is inside a secure parking garage so we can leave bags on the bikes during the day. It'd be a lot less convenient if you had to take it off and schlep it to an office.

For a dedicated cute bag I have some smaller items from this company and like them - and I think this bag is much cuter than the average covertible pannier - www.pocampo.com/collections/trunk-pannier-bags/products/bergen-laptop-pannier

[CrazyLucky]

That one IS cute! Thank you for the suggestion.