I've been thinking about switching over to Apple for some time now. However, I've got a Windows desktop at home AND my trusty little 13" Fujitsu Lifebook (S-Series) AND the machine I use for work (company issued) is a Dell. The Fujitsu is an older machine with only a 1028x780 screen and that is slightly annoying and my desktop is also four or five years old, but they work fine. My only real beefs are with Microsoft and with the small hard drive (60GB) on the Fujitsu, which has become limiting only to the extent that I have to keep most data files on a USB hard drive unless I want to swap out the laptop hard drive for a larger one. Basically, IF I switch over, I need to have the new machine be my one-and-only. I don't see myself dropping the coin to get a Mac desktop and the MacBook both. But the 13" MacBook Pro is limited (no dedicated graphics, etc.) for use as a desktop and I'd prefer to have less weight to travel with. Plus there is the issue of switching over all of the freakin' software I have (actually not all that much, I suppose, as long as some data files are transportable between Mac and Windows versions of certain popular software. I'd also not be able to load any more of my own software onto the work machine. So, what to do . . .
The Apple's are usually going to be more pricey, but iof you spec them out on a more comparable level, the difference is not that much (meaning often the ads, like the current ones where people are going in and buying a PC and get the money are machines that are not quite the same features, when features are matched up more apples to apples, as it were, the difference is not as much.)
Usually most files are switchable between PC and Macs. Of course not all are, but most standard apps work fine. Some things are PC only. I do run run some PC programs in Paralells which works pretty well for the things I use, but nothing major on the software side. I love Macs, but I would not rely on a Air (or any laptop of any brand) as my sole machine for working based on what I need to do. I have a 15" and 17" which I really like, and have used them for extended periods of time when travelling to do work, but when I can back to my newest tower there is alot more Power. Of course when I got my 17" Laptop, I did find it better than my older tower that I was still working on. Even a refreshed (Applspeak for Refub) iMac may make life alot easier. A refreshed Tower and you will be pretty happy. Alot of it also depends on what software you are running. Obviously Photoshop, Lightroom or similar things(?) You could list what you use to get a better sense.