It's not really ready for use as a primary OS by the general public although it's already quite stable so if you're feeling adventurous and are knowledgeable about the environment you could. They still haven't announced a firm date for R1 but rumor has it it's fast approaching.
You've probably seen this but in case you haven't here's what they say:
We do not have a firm release date [for R1] . Haiku development is advancing steadily, and when a stage is reached where the development team feels confident about setting a target release date, an official announcement to that effect will be made