Edit: Also note, the 2013 Mac Pro only supports Windows 8. Any system that comes pre-installed with bootcamp 4.0 or above will be hard to install windows 7 on, if it is at all possible. I don't know if the new MBAs come with 4.0, just a fair warning if you are planning on buying a new MBA.
Not sure where you got your info. First off, the current version of bootcamp is 5.x.x, and it still DOES allow you to install Windows 7, depending on the machine. Every mac model needs Windows drivers that make it work on the Windows side.
The problem with the new mac pro is that Apple decided to only write drivers for Windows 8.
I'm confused by the win 8 bashing. If you disable metro, it's virtually indistinguishable from win 7, and reputable reviewers report that win 8 actually manages memory and resources better than win 7. I researched the questions on PC forums and came to the conclusion that win 8 was generally recommended over win 7 and you should just use a start menu instead of metro.
Does it matter if the Windows I use is 32 or 64 bit?
Huh? If you have a gas engine, use gas, if you a diesel engine use diesel, don't mix! What is your processor? 32 or 64 bit, answers your question.
So it does matter? If I put diesel in the tank of a petrol car, it breaks the engine. My processor is 64 bit so if I use Windows 32 bit it won't run?
On a straight Windows machine a 64 bit processor will run either and not break (albeit not as sufficiently) is that the same when using Windows on a Mac?