The 2.0 version is currently still in Beta (this is the latest one), and the 1.0 version is stable but basically deprecated (The 2.0 SDK is *not* backwards compatible, and will be the only supported version moving forward).

So yeah, it's kind of an awkward situation they've put Pebble developers in, the recommended SDK to use is still in Beta, and apps built on the stable release will be obsolete soon.