Because so much of Dropwizard is glue code, the way in which things are created, configured, and wired together could use a bit more love.
I'm willing to dedicate some time to completing the ground work on the MetricsRegistry/HealthCheckRegistry case you mention above (i.e., removing dependency on static factory methods).
Are you looking at only factoring out the static factory methods (ala Metrics.newTimer(...)) to meet this goal, or are you also looking to allow the default registries to be replaced?
I've started working on Guice. Should the Guice AbstractModules be part of the environment's collection or the service's collection?
I actually have a GuiceContainer w/ mixed Guice/Jersey lifetime management working.
+1 for using some Guice DI love. Was just thinking about this myself.