iPhoto upgrade necessary?

Apart from some cool new features in the more recent versions of iPhoto,

is there any serious disadvantage of not upgrading to the latest iPhoto?

I like to order the "classic" book covers (canvas wrap with photo). so I keep working with iPhoto 6.

It works great, just asks for the occasional thumb cache rebuild.

I am just curious, if there's any disadvantage to my photo files when using an older version.

I really just use iPhoto as an image archive - and print the occasonal book ...