Is Kata important to Karate-Do?

I believe Kata is important, it is one way of remembering and applying what you learn. The better you get with individual techniques the more you appreciate the application and grouping of these when performing Kata. Kata is something that is never mastered only improved upon. The fun is knowing you are improving and becoming better at understanding the application and delivering the techniques.

Should you practice many different Kata (as there are lots) or just focus on a few ?

I think all. use a home work list and work down.

I agree. I've found that by using a list of all the Kata, or all the Kata that i was required to know for my grade, that i was having to practice the ones that i didn't like, as often as the ones that i did. I think that it is easy to become good at the things that we like, the true test of character is to do well at the things that we don't enjoy. The more practice i put in on my least favoured Kata, the more i grew to like them.

Yes, Practice, Practice, Practice. Everything is difficult when we don't know how, then it becomes easy, but then we start all over again, a never ending challenge

Kata is what your study has allowed you to see it as. Once you start to gain info about Kata that is gained from experienced Instructors you will find that Kata alone can be a lifelong study = Fathom the dance (I assume you know the poem)

Only for Dan Grades?

I don't know the poem.

Again kata; why it is so important:
It is mistakenly thought that we start with Kihon, then Kata and finally Kumite, this is not strictly true, it is Kata that is the final solution. Gichin Funakoshi, founder of the Shotokan Karate-Do stated “Once a form (Kata) has been learned, it must be practised repeatedly until it can be applied in an emergency, for knowledge of just the sequence of a form (Kata) in Karate-Do is useless” Hence it is sometimes said it can take 10 years to learn a Kata! If you think about it, all Kumite attacks are done from the forward stance (Zenkutsu- Dachi) or (Jiyú-Dachi) all of these are long Karate stances. Just when do you get attacked by a Karateka? In real situations people do not assume a stance and attack from a distance, they usually attack from close up, and not with a Karate technique. Kata was never designed for Karateka V Karateka. So then we have the Bunkai and more….. I absolutely agree with Ian Abernethy (Read his book ‘An Introduction to Applied Karate’ by Iain Abernethy) The four Stages of Kata.