I only got the Creative Bundle (for $99) and I’m happy at that $10/each level.
But I’m hesitant to get the Mix Edition or Diamond, as they will undoubtedly grow larger with (many) more native titles.
As for the Ultimate, that’s another story. If you buy it (after registering some hardware) you’ll get it all, including future native releases.
Then again, UAD is on a roll, and who knows where they’ll land. I do consider a possibility that UAD 12 will go very low, but when…
On the other hand, many plugins aren’t native yet and those are the ones I’m interested in, so I might wait.
So for now, I’m thinking I’m fine with the instruments (while only missing the new Rhodes) and a few special FX like the ones on the Creative bundle.
As for mixing and mastering plugs, I’ll stay on the fence.
Hope this rambling helps somewhat.