Achievements are absolutely a big deal. It's an additional scoring metric that adds another layer of playability. iOS features this nearly universally with Game Center, why shouldn't we have the same thing? Given that Xbox Live pretty much established the concept, it makes it especially absurd that it isn't being pushed harder in Windows Phone.
The underlying concern is that it doesn't paint a positive picture for the future of the platform. Keep in mind that while Windows Phone 8 is only 4+ months old, Windows Phone 7 has been around for 2 years. The core of the OS has changed, but superficially it's the same environment. Promises that were made early on have not been delivered on. Worse, things seemed more promised back then than they do now. And logic would have dictated a much stronger app lineup to coincide with the launch of WP8.
Things may not be as bad as some make them out to seem, but there is still cause for concern.