Try bringing both for a few trips, but try to just use the iPad, and only use the MBA if you need to. See what happens.

As many have said, it depends on the trip.

I just got back from Hawaii, and was packed to the gills. I knew it was going to be raining (it's Hawaii afterall) so I had to bring more clothes than I would normally. Plus, it's Hawaii, so I had to bring my camera gear, which requires multiple lenses (I only brought 4 of my 6) plus a tripod, flash, charger, lense cleaner, external batteries etc. Add on to that laptop and ipad, charger for those, and phone chargers, etc, you get two very packed bags. If I'm just going to NorCal or something I could do it in one bag. If I'm going to Vegas (I do quite a bit for a night or two) then I need to take more clothes to avoid smelling like an ash tray, but can take smaller bags since I don't have camera gear.

I have a weird opinion on this because I work the ramp. Now, mind you, I used to check one, then when it went to charge, I went to carry-on only. Now that my credit card lets me check one.. I check my carry-on. I never pack anything important in it, because I know how it is on the ramp and in the back. I like it because I don't have to drag it around the terminal when I'm making a connection... or what not. I don't have to worry about planeside checking it for that little RJ segment and waiting while the rampers bring it up.

The one thing I will rant and wish everyone would heed is: Please use appropriate sized luggage!! When people overstuff their checked bags, it bulges the sides. It doesn't stack nicely in the cart or in the bin. Additionally.... I'm afraid that if I sneeze at it, it will burst at the seams. The same goes with large empty luggage. It crushes under the load and then the whole stack goes. Additionally, the weirder sized bags just slow the whole process down. Simpler is better. Less wheels, less weird shapes, the more square it is, the easier and faster for the ramp to process it.

+1 - When we go to St. John one bag is for food and one for snorkel gear. We carry on our clothes. :-)

I couldn't do it. I need too much work stuff from my laptop.

In addition, I just couldn't.

[that was supposed to be an embarrassed emoticon]

recently went on a three-week china trip including shanghai, wuxi, hangzhou, guangzhou and beijing.
All in a carry-on. It is very easy actually, every single decent hotel has laundry nowadays:p
As a male it is really easy as you can use a few items variations to make up a huge variety of looks. white and blue shirts, 3 ties, blue suit, black and khaki trousers, that's about it.