Workbench 3.5/3.9. Worth upgrade?

[itix]

You can get all Workbench add-ons from Aminet. There are some new components too but if you are mostly using mod players and Deluxe Paint there is nothing new to you. Some programs work better with Kickstart 3.1 so upgrading might be useful but not mandatory.

Edit: though, on 3.5/3.9 you have everything on one cd which is quite nice if you must reinstall everything (for whatever reason).
Edit2: WB 3.9 enables new icon formats: newicons, glowicons and png icons (needs additional patch)

[itix]

But as you have a Blizzard turboboard you can use blizkick to softkick ROM3.1 in your machine if you like.

That would be piracy if you dont own legal ROM.