Does the windows 7 run well under mac hardware?
It runs about as well as a PC that runs Windows by default. There are some quirks, such as there only being one control key on the keyboard. The two command that you use like control in OS X are Windows keys. The trackpad is inferior. There is a hacked set of drivers called Trackpad++ (there's a thread in this very forum about it), but I found the program to not always be reliable. With the stock drivers, it's functional, but not nearly as elegant as OS X.
The Retina Display does not scale properly with Windows 7. You can get a reasonable approximation by setting the display to its native 2880x1800 resolution and using a zoom level of no more than 199%. Windows 8.1 delivers much better support for HiDPI displays.
If your system has a discreet GPU (NVIDIA GeForce GT 650M or 750M), it will be active all the time in Windows. There is no automatic switching as there is in OS X. As such, battery life is greatly reduced. If you only have an integrated GPU (Intel Iris/Iris Pro), battery life is better, but still not up to OS X levels.
Does windows 7 do a good job emulating XP environment, or is there a better version of Windows to do this?
If you want to emulate Windows XP specifically, you can use Parallels or VMWare Fusion in OS X and get pretty good results. This naturally requires that you have an XP license in hand. Windows 7 Professional and Ultimate come with the ability to download a Windows XP virtual machine for free, no separate license required. Do you require specific software that is not compatible with Windows 7? Very few applications today fall into this category.
Are the drivers for keyboard, sound and such installed automatically?
This is a separate installation. There is an option when running Boot Camp Assistant to use a Windows .ISO file to create bootable install media on a USB flash drive. By leaving the box checked to download the Windows Support Software, BCA will also add the appropriate drivers to said flash drive.
What does the selection screen for loading different partitions look like?
Not exactly sure what you're asking here. Once you've installed Windows, your Mac will boot to it by default. You can select which operating system you want by holding the option key after you've powered on the system. To boot to OS X by default, start it, then go into system preferences/startup disk and select it.
