Writing for standards compliance is great when you don't care where/if your code works, what browser do you use that perfectly adheres to all the standards?
I use resources like MDN and some automated testing tools to make sure the subset I use is properly implemented on all major browsers (all but IE <= 8, which really sucks at it).
But, subset or not, what I write is still 100% standards compliant code, in almost every project I'm involved with. I avoid as much as possible writing vendor specific code.
The result is I hardly ever get a complaint about my code working on one browser and not working on another.
