Ok, my experience....
VA + HCS Voice packs are awesome. I have about a dozen.
ASTRA is (or was) the most comprehensive and is full featured (things like quotes from Steven Hawking etc which not all packs have).
As others have said, you need key bindings for pretty much everything and mine have been set up way before HCS included some binding "help".
The hardest part of the whole she-bang is getting Windows to reliably interpret what you say...so you do need to go through the Windows based voice training.
I needed to do this a half dozen times due to my accent...YMMV...find it here...
The next hardest part is remembering what commands you can use, so download and printout the pdf which comes as part of the downloaded pack.
Cheers
Clicker