I had used Opera on my Xoom tablet for 6 days. The Opera app is more faster and safer than the stock browser. I really like it and want to set it as my default browser.
To reset Opera as defaullt browser on Xoom, tap Settings > Manage All Apps > select browser > Clear defaults. Then open Opera app and click set as default. It will bring a popup window to let you choose the browser you want to use, choose Opera.