I bought VST Live as I have recently moved from windows to an iMac, and I wanted something lightweight to run VSTs rather than me having to fire up Cubase all the time. (I still have my windows laptop for live work running with Cantabile).
The Steinberg product is currently very flaky and unreliable, although they are emitting fixes at a fair old rate and the product is getting better with each iteration. They also seem to be very responsive to issues raised on their comments board. Also, unlike others here, I have always found Steinberg very quick to respond to any problems I have had with any of their products.
So for me, it does a lot of what I need it for on my desktop machine - i.e. host VSTs. It is nowhere near as sophisticated as Cantabile, but it does at least run on Apple machines, which of course Cantabile does not.
I would certainly not want to use it for live work at the moment, but I am sure that given a little more time, it will become a capable piece of software.