Yeah, even with m/k Voice Attack is really handy for fast switching between engines, systems and weapons as you're fighting, as it's quite tricky to find a good keybind for those if you're using the m/k (since all the more "useful", easy to access keybinds you'll probably already be using for flying, natty manoeuvering and firing), and given how crucial to the combat gampelay in ED being able to switch systems quicky while fighting is, it's worth fiddling about to find a good solution, and VA is a good solution to that problem.
And that elitedangerous voicepack is great. A.S.T.R.A. is a pretty high quality Evona voice, treated with fx to sound a bit robotic like the onboard voice, so she blends in nicely. Much, much more atmospheric than the rather bald-sounding Microsoft voice TTS by itself (although of course the downside is that the responses are "canned", and can't be tailored). The Basic profile has all you need for piloting, and the built in responses (i.e. the things they've recorded the Evona voice+fx to say) are just fine, while the Full House profile has lots of other fun stuff so you can sort of chat to A.S.T.R.A. almost (not really, but there are tons of questions you can ask her and she responds).
And the great thing about Voice Attack, either with or without a voice pack, is that you can tailor your commands (e.g. you might prefer to say "landing gear Astra", instead of "deploy landing gear", you can just edit that command in the profile and add whatever you want to say to the list of voice commands.
The only thing to be aware of is that the voice pack has certain keybinds built in (mostly using numpad commands), so for that purpose they give you a default keybind, which you put in the right place in your Users directory (they give you the instructions). But this also means that you might have to re-input any special keycommands you put in (e.g. I use Mouse3 for boost instead of Tab, so I had to change that in the default keybind - the one the voice pack people give you - from in-game, and then change the relevant command in the voice pack profile). With other commands you can just use the second keybind slot FD gives you to add your own keybind to the built in one, if the built in one is using a key you wouldn't use for your own keybinds.
Maybe sounds complicated, but it's all fairly easy and straightforward and quick to fiddle about with and fine-tune once you understand what's going on, and it's fairly well documented, both the Voice Attack program itself, and the A.S.T.R.A. voice pack.
I'd say that both VA and the voice pack are worth the purchase price, they're not game changing, but they're a fun, useful addition, well worth the small amount of money they ask for.