Already in a release Candidate, WordPress 2.0 will be finally coming out this week. However, those interested to download and use WP2.0RC may do so here. Just be carefull as it may not be compatible with your themes and/or plugins.
Even if the final stable release becomes available, I’d suggest waiting a couple more weeks before upgrading to 2.0. Besides, there aren’t any security holes in 1.5.2 so there’s no rush to move up.
However, if you’re installing in for the first time or using it on a fresh blog, the WordPress team would be happy to get your feedback and maybe identify some new bugs in the process.
As what we’ve learned days ago, if it ain’t broke… don’t fix it.