I haven't yet made the plunge into iLok territory myself. If I had occasions to take my plug-ins from computer to computer then it might be something I would get. I don't yet have any reason to transfer plug-ins regularly so I just use the registration key method (and print out the keys for a paper record).
When I started doing the computer recording/mixing thing I didn't know squat about plug-ins. After poking around the internet for awhile and doing research on plug-ins I realized that a lot of the high-end, brand name gear manufacturers who came out with plug-ins (TC Electronics comes immediately to mind) made them compatible only with Pro Tools and sometimes even with their own proprietary cards (as you can see with UAD).
If a plug-in comes in VST, VSTi, or Direct X (a Microsoft protocol dying a slow death even though it is viable) then it is compatible with Audition.
You should check out the plug-in lists on this forum and on the AA forum for some good advice on plug-ins.
Besides some of the nice free VST plug-ins I've found I'm partial to the plug-ins made by
PSP Audioware, a company out of Poland. You can get some fully functional demos.