- DON'T DO IT: Any major OS update is bound to cause some disruption, either by potential software incompatibilities or just the added time it takes to become acquainted with the new features. Considering the amount of effort Apple is putting into Jaguar, it may be a near seamless upgrade. However, if you use your Mac for critical applications (work) and can't risk having things changed (even slightly), perhaps you should wait a bit and let the gung-ho early adopters test the waters first.
- DON'T CARE: On the other hand, some OSX users may really be looking forward to the new features of Jaguar and might even appreciate the opportunity to do a fresh install to 'clean things out', so to speak. If this is you: you don't have any irreplaceable data and don't mind re-installing all your apps from scratch, then go for it!
- BACKUP DATA: If you have important data installed on your system but are planning to upgrade to Jaguar anyhow, you probably want to make a backup your data files, at the very least. In particular, consider backing up the contents of your home directory (i.e. /Users/myname) to a separate volume (either another partition or an external device). For example, I make it a point to backup my Entourage v.X email whenever I do an OSX re-install. Entourage keeps all that data in the '~/Documents/Microsoft User Data' folder, so I periodically copy the entire folder to an external drive for safekeeping.
- BACKING UP EVERYTHING: But if you're like me, you probably prefer to do a clean install of a new OS, re-install your apps, then restore your data. This method carries a bit of risk if the Mac you're upgrading is your primary work machine (see DON'T DO IT). One way to minimize downtime due to potential upgrade problems is to backup/image your entire existing OSX volume. This provides a safety net that will quickly allow you to recover from a failed install and revert back to a working system. True, you won't have an upgraded OS, but it will at least allow you to return your Mac back to a working state (until you can sit down and devote more time to investigating why the Jaguar update work quite the way you wanted).
Two solutions (I'm sure there are others) for backing up up your entire OSX volume:
1) Retrospect Backup Express. A commercial backup app with an excellent reputation that appears to be extremely easy to use. However, this is a file-based backup system, and it may not be able to restore a blank partition to a functional state (anyone know for sure?).
2) Mike Bombich's HOWTO and/or backup app. This is the method I use. It does require some work, a separate bootable OS9 or OSX volume, Apple's ASR utility and a few other apps (Diskwarrior and NUM are helpful), but I was able to backup my entire working OSX volume to a 3.3Gb image file. Now if something goes wrong, I can quickly restore my system in about 15 minutes instead of spending hours re-installing Apple software updates, user apps and data by hand. I'm planning to do another such backup just prior to installing Jaguar next month.
[Editor's note: Good advice to keep in mind as Jaguar approaches...]

