me, me, me
Well, everytime, Every single time I post something here I feel like I am making vanity posts. So.....
Here it is let me tell you about my experience.
I installed Jaguar as an upgrade to OS 9. I was amazed that it worked so well. Easy to install something that I would think is very difficult. There was a problem though in that my HD is very small and having two OS hogs it all.
Something bad happened, I had to erase my HD after a year of steady use of OS X. I haven't used OS 9 for about that long too. So when I did a fresh install of OS X on my drive. I didn't install OS 9. I saved a lot of room on my hard drive and picked up some performance.
So, the answer to your question. If it is possible, do a fresh install on your erased HD. But I am sure that a upgrade will be available, and it will work very well. I personally will be doing the upgrade. I won't be erasing my HD unless something really messes me up.
WHAT WENT WRONG-
note, I had two seperate users on my hard drive. My side took up too much space and the OS wouldn't open up the other users side. So, I thought making the side that wouldn't open up the default log in user would open up the blocked side. Opps. I couldn't get into either side. Locked out! Damn. I had to either do some heavy terminal trickery or erase and install. It took all weekend to get back up to speed. Hello, lost shareware registration emailing.