iLife does not come with the OS.
So, iLife 08 does not come with 10.5, nor does 09 come with 10.6. The iLife apps are not part of the Operating System. The confusion sometimes arises because they both come with a new Mac.
So, to be clear, iLife requies a separate purchase from the Operating System, regardless of which version you are using.
iWork is similar, except it doesn't come free with news macs (a time limited trial is installed) and always requires an additional purchase.
The Box Sets are therefore better value than purchasing the elements singly.
I plan on placing iLife 08 and iWork 08 in a folder before I upgrade, does anyone have problems running both 08/09 ?
I'm not sure what you hope to gain by this. But it is worth noting that once iPhoto 09 has upgraded your iPhoto Library iPhoto 08 will no longer open it.
Regards
TD