Thats good, I think. BIOS flashing is something that should never be taken lightly, so fear is likely to ensure you research the subject fully before doing it. As long as you do it properly and well, everything should be OK. I just think there is a tenancy for people to think its as easy and safe as installing new drivers- it isn't and should be done with care.
EZflash is, I believe the BIOS based programme (don't trust me! check!), not the windows one, and therefore should be OK. I would certainly not use a programme that will flash from within an OS, or one that will automatically download. Go to the Asus website Carefully check which bios you want for your board, read up online about that bios, and put it on a USB key. You can then flash from within your BIOS.
Just make sure you do the research and you should be fine.
As people said, it might not be worth taking the risk, just because you want the 'latest version'. Only do it if there is actually something that you need! (e.g. 45nm compatibility)
Its not an overwhelming risk, it'll be fine if you do it with care and research, its just that generally people are not scared enough, hence the slightly overly careful posts that everyone has made.