I'm running WinXP Pro SP3, and Opera 11 runs fine. However, it is not my default browser(Firefox), I guess I have it installed out of curiosity. It is interesting to see some sites display differently with Opera, Firefox, and IE8, though I don't spend much time with it. Immunizing Opera is like hitting a moving target, with it's constant shifting of file locations, and such.
FWIW, Opera 11 doesn't generate the file opera6.ini at all. In C:\Program Files\Opera\defaults is plugin-ignore.ini which SpyBot Search & Destroy alters for it's immunizations of plug-ins in Opera 11. This works for all Windows users on the machine, when SpyBot S&D is ran as an Admin with the Allhives switch.
SpyBot Search & Destroy does really need to be updated. It is now getting disparaged in most other security programs forums.