I may be a little late posting this reply, but I have been busy.
As Marvin advised - Make a backup!!! I have, actually, had to rely on my backup this year because my new .est became corrupted. Ended up that I could no longer add pushpins.
After the backup, it is as easy as opening the old .est with the new ST2009. Confirm the conversion and then save the new file. I even add 09 into the name, so that I don't get confused.
Also, as was mentioned, if you relied on the ST pushpins, they will be converted to plain pushpins. My use of pushpins is for house numbers. Fortunately, I had created my own set for the lower numbers. I just have to convert the upper numbers now. Of which, there are a lot less of them.
And one final advantage of opening the old file and resaving, is that the push pins you created, if any, will be sorted as you had them. As I said, I had created my own number set. When I would copy a pushpin set (like the one I have called Streets that I use to mark previously unnamed streets), the program would not have the pasted pushpins in order as I had. I had used letters to mark the streets, using the first letter of the name.