Opera 8.50 was recently improved to remove the adbar on the free version.  So far the new version is working well and presents no conflicts with IE 6 SP2 or Mozilla Firefox 1.5. 

Release Note

This release is a recommended security upgrade.

At a Glance

• Advertisement banner removed
• Registration options removed
• Updated end-user license agreement
• Browser JavaScript fixes broken Web sites on the fly

Changes since 8.02

User interface

• Removed advertising banners and all dialogs and menus related to advertising, registration, and license codes.
• Solved issue with Opera reverting explicit user setting to use program as handler rather than plug-in.
• Removed support for branded banners.

Security

• Fixed issue reported in Secunia Advisory 16645: Attachment URLs now used instead of cache URLs for viewing attachments.
• Fixed drag-and-drop vulnerability allowing unintentional file uploads. Issue reported by mikx.de.
• Improved handling of must-revalidate cache directive for HTTPS pages.
• Fixed display issue with cookie comment encoding.

Miscellaneous

• Included Browser JavaScript by default. On first run after install/upgrade, Opera will fetch a fresh browser.js file and start using it.
• Multiple stability fixes.

Download Link for version 8.50: