Downsides of using Windows on a Mac Please do not comment on how using Windows itself is a huge downside. After several years using OSX, Linux and Windows, I can say that working on the latter OS is best for my needs.

I do own an iMac (27", mid-2010) however, and I am aware that I can install Windows 7 on it w/o using Bootcamp. Now, are there any caveats in doing so? E.g. I noticed that the iMac is heating up more than it used to under OSX. Maybe the arguably annoying abundance of hard-disk accesses under Win7 is a reason for that. 
Could this be a danger? Are there other issues known to SE users here? 

summary: any caveats in using Win7 as main OS on an iMac?

EDIT: These helpful answers indicate that in general it might not be such a great idea to extensively use Win7 on a Mac because the hardware might wear off faster due to sub-par Win7 power management (compared to OSX).
Windows Vs Mac wars aside, it makes a lot of sense to use a Mac as a Windows machine. PC World or PC Magazine (I always get them confused) named the MacBook Pro the best Windows machine not so long ago. Their reasoning was that Apple includes the right drivers for the different hardware components that they ship on the Mac. I don't think that means the latest drivers, but the right drivers nonetheless. 

@Rabarberski speculates if Apple does not want to invest too much time and money developing good drivers. My take on this is that I don't think Apple develops their drivers, they just work with a much limited number of components and that makes including all necessary drivers in BootCamp possible (For instance, there's only a handful of different video and sound cards that the Macs have shared over the last few years). My theory is that Apple doesn't issue repeated updates to the BootCamp driver set precisely because they don't need to--the ones included work fine for all of their Mac hardware configurations. 

Before switching over to the Mac, I used PC's from Acer, Compaq, HP, Dell, Toshiba and Lenovo. On each one of these systems, drivers were always an issue at some point--even the ones included in the system restore disk. Using Windows on the Mac has been the exact opposite experience and I highly recommend it if Windows is your thing. I develop software for Windows and the Mac and I dual boot using BootCamp. I am seriously considering keeping my current MacBook Pro as a Windows-only computer once I get my next Mac. Hope this helps.