One of the biggest performance caveats to any MBA and any 13" MBP (retina or otherwise) is it's lack of discrete graphics, and lack of a quad core CPU. I own and love my 13" MBP, but that's because it fits like a glove and does what I need it to do, most of the high end stuff I do on a quad core desktop.
That said, the retina is cool, but budget wise you really may be better off with a classic. It's up to you, of course, but for $1,800 you could get;
The same 13" form factor MacBook Pro;
13" non-Retina MacBook Pro: $1200
512GB Crucial SSD: $400
16GB of RAM: $100
That puts you at $1700 for a machine that will perform as well or better than the retina, with more storage and more RAM than what you'll end up with for $1,800. This is the configuration I went with.
OR, you could move on to the 15" for a boost in performance (Quad Core + GPU)
15" non-Retina MacBook Pro:
15" non-Retina MacBook Pr: $1500
256GB Crucial SSD: $200
16GB of RAM: $100
Here you have a real performer for $1800 that will be a champ, and run CIRCLES around ANY configuration of 13" retina or non retina. Of course, you give up a certain amount of portability, so that's up to you. I think the 13 fits like a glove, but the above listed system would scream. If you need more storage, you have two options. One is to buy an optical drive hard drive bay ($20) and put the stock drive in there as a second 500GB drive (or even configure it as a 'fusion drive'). The second is to simply up your budget $200 to get you to the 512GB mark. You could also save a little bit by not upgrading the RAM and sticking with 8GB, then you're at $1900 for a 15" non Retina with a 512GB SSD and 8GB of RAM.
Just my $0.02!
