"A common problem online is that many websites are not based on standards, but either use outdated browser sniffers, a popular method for addressing different browsers bugs and quirks including Opera, or use nonstandard or simply incorrect code. The websites are often only tested in Internet Explorer, with the correct display reliant on the Internet Explorer rendering engine, which is tolerant of code that does not conform to official standards. Nonstandard websites have caused problems for Opera and its users, as they give the impression that the browser is broken."
The text problem you mentioned only happens in the current preview version of Opera 9. Not in any other version.
And the problem with webstandards applies to ANY browser besides Internet Explorer. This includes browsers using Gecko engine (Mozilla FireFox etc).