>From the HBase perspective, life is complicated by the need to support running on multiple Hadoop versions. Current HBase trunk is really targeted at 0.20-append, but I'm also working to add 0.20-security (or 0.20-append-security) to that. And there have been questions (though I'm not sure a clear decision) on support for 0.21 now that it's released. And obviously I can't predict where things will stand in the 0.22 timeframe.
Sounds like the new framework will have some great stuff allowing us to strip out some of the HBase code we've added for metrics (built-on JMX support), which would be great to make use of. But until HBase is targeting only 0.22+ I don't think we'll fully be able to convert to it. So I'd vote for option #2 to allow us to make a phased transition. --gh
