If you have full TH3 and don't need to pay VAT you can have THU for 49$ 49 EUR (sorry my bad - bought on TimeSpace, just checked my orders, but cannot see this offer anymore there) .
Despite of some new flaws (like making looper from poor to terrible) it is adding some valuable things like more amps and stomps. More possibilities to change character as valve select. Also RIG player which is promising some Kemper profile compatibility in future.
Here are some samples from Slate (smaller a little limited of THU will be added to Everything bundle soon) :
www.stevenslatemedia.com/thu/RockA.wav www.stevenslatemedia.com/thu/RockB.wav www.stevenslatemedia.com/thu/BluesA.wav www.stevenslatemedia.com/thu/BluesB.wav
They are Kemper vs THU comparison.
And after THU install TH3 is still working. So from my point of view I don't regret I have upgraded. Despite as EU citizien I was forced to pay additionaly VAT so my price was 60$ 60 EUR (sorry my bad - bought on TimeSpace, just checked my orders)