Yes, but you have to pick your battles. Unless you run an already ginormously successful site which can afford a substantial loss of traffic, then being dogmatic about web standards will only hurt you and do nothing to drive people away from non-standards compliant browsers.
... not sure anything is likely to drive people away from standards compliant browsers, maybe just sites that won't render in less capable browsers.
I reckon the user would blame a poorly rendered site on the author/owner rather than the browser.
Standards are the goal, and it's never been closer. However,
interoperability is more important. Writing markup, code and styles to the standards and provide at least an accessible level of operability to the less capable user agents.
