Mook,
The greatest advantage to the WUP is that
every dollar you spend on it you can use to
buy more Waves Plugins.
You get a voucher for the dollar amount you spend
good towards up to 50 percent off of a bundle
or 25 percent off of a single plugin.
AND you get whatever new version may come out during
the period of your Update plan and any new plugins added
to a bundle you own at no charge.
To me, if I'm planning on buying a new bundle from Waves,
I will investigate my WUP Options and then purchase the WUP
and use the voucher to help buy the new bundle or plugin.
That way I'm getting my NEW Bundle or Plugin AND basically
getting the WUP for free, so it's a win win.