I recently replaced added a Bent Up Cycles Aero Bag to my Corsa, replacing the home made "speed" bag that I've used all Summer.  Here is my review.
 
Pros:
 
Capacity.  While most mfgs love to list the capacity of their bags in Cubic Inches, that doesn't help unless you've measured everything.  After yesterday's ride I emptied my AB and discovered what it will really hold.
 

Riding jacket
Arm and leg warmers
Skull Cap
Balaclava
Gloves and glove liners
Spare tire (650c Gatorskin)
Bicycle pump
CO2 pump and 2 cartridges
2 spare tubes
Tube patch kit
Tire levers
Tire boots
Small bicycle multi-tool
Rear derailleur cable (tandem length)
2 Cliff Bars
1 small rock ??
Wallet and Cell phone

 
Clearance.  I tend to have my seat laid back, which is why I can't use any of the Bachhetta bags without rubbing the tire.  I had plenty of clearance with the AB
 
Zippers.  The AB has dual zippers, unlike other bags which only have one that must be run all the way to the front edge of the bag.  I prefer that style.
 
Safety.  The AB comes with a reflective strip around the bag, another good feature.
 
Removeable bags.  The AB has an internal velcro strip and comes with two small zippered bags that can be used to hold tools, wallets, etc. for easy access.
 
Cons:
 
No Mesh pocket.  I use speedplay pedals, and every other bag I've tried has external mesh pockets that are perfect for storing cleat covers in, so you don't have to open the bag to get to them.  Time to get out the sewing kit.
 
No hose feed through.  For those who prefer bladders instead of bottles, you would have to leave the zippers open a little to let the hose out.  I am one of those who prefers the bladders so I can drink while descending.
 
The Jury is still out on:
 
Side bottle pockets.  The main feature of the AB is the two side pockets for holding bottles.  Due to the location of my light bar I cannot place the bottles into them while riding, so I am not sure how useful they are without seat mounted bottle holders as well.  Having the ability to carry four bottles is good, I'd just have to stop and swap at some point.  Those pockets could be used with a bottle sized tool pouch.
 
Overall construction.  The AB looks good out of the box, let's see how it looks after a full riding season.
 
Cost.  It is a bit pricey ($139 plus shipping), but it let's me carry what I need for the winter season without having to change my seat position, so for me it is worth it.
 
 
 
 

My pink bag is the first run of the Aero bag.  I definitely like it much more than most bags I've tried, including the brain bag.  It's theoretically smaller than the brain bag but with the design of the bag I feel like I can fit more into it.  It's certainly more accessible.
 
It's designed to be a race bag, not a rando bag.  If you use the bottle holders, I recommend just using it to swap out a bottle on the bike instead of trying to get it in and out, but it's still not much fuss.  That's why there's no pockets.  I love the dual zippers for sure.  Shouldbe as durable as anything else since it's essentially the same material.
 
Bryan, if you like the bladders, as I do, many of us use the fastback LS for them insteadof our rear bags.  The bikes seem to like the weight there anyway, and it frees up a lot of bag space too.
 
I will keep using my brain bag as my winter/rainy bag, and my BU bag in the dry summer - that way I keep it looking fresh and neat.  I'd hate to get mud over my nice pink gear!

Quote from Killer Bee on Nov 30^th, 2009, 3:21pm:

 
I saw one write up on it stating that it was a bit loose on a carbon seat, and the owner solved that problem with Velcro, so I'm guessing that it's not snug.  If you bring a carbon seat to the Christmas party, we can check the snugness then (or you could borrow it between now and then and drop it on your bike)

Most carbon seats are narrower than the Euromesh. My CCK is quite a bit narrower. So, you can expect a more loose fit. Even with my Euromesh, I added velcro to my brain box so it wouldn't slip.

Quote from Killer Bee on Nov 30^th, 2009, 3:21pm:

 
The AB is a fairly snug fit on the Bacchetta carbon seat. Snug enough to prevent lateral movement of the bag. However, it is not snug enough to prevent the bottom from swiveling slightly (the back end of the bag moves vertically about 1/2 inch). On rough pavement the plastic sheet-reinforced bottom repeatedly hits the back of the seat and makes a noise. May not be objectionable to some, but it is to me. I plan to install velcro to stop it from swiveling.

Quote from evblazer on Nov 30^th, 2009, 9:45pm:

 
EV, that' s right, Ray has a carbon seat with the aeropod.  I'll have to ask his thoughts of the aeropod on the carbon seat. The downside(besides the price) is that the aeropod doesn't have the exterior bottle holders.