RebelYell --
Congrats on the new 600! I think you'll enjoy it! You don't "need" to do the update. The machine runs quite well with the original software. The updates are largely just "tweaks," so no reason feel like you need to rush to load the latest software. One feature that is included in the latest update, though, that is helpful to 600 users in particular, is that you now have an additional "brightness" level for your backlight. If you do any night hunting, the additional, "medium" backlight setting is a welcome change.
There are ways to find out if you are running the newest version of the software without connecting the machine to your computer (such as whether you have that additional backlight setting). But if you simply download the Minelab Update Utility, version 2.0 or whatever (I think when I did it, it was like 2.0.3 or something), and connect your machine, it will let you know if you are running the latest software, and if not, will allow you to install the latest update. It's pretty quick and easy. V. 1.5x was the first version, 1.75x was the second, and now 2.0x is the current, latest build.
Steve