I personally never liked AA2 for transfer and restoration work and tended to stick with 1.5. By comparison I now do everything in 3.0 and rarely look back. The new tools for FSE work are worth the upgrade alone...
I did the same thing, I have 2.0, but stuck with 1.5 for most of my audio restoration work. However, I will get 3.0 for the new mastering tools.
Do you recommend the full disc or the upgrade download? Will the upgrade give me any problems?