Following the release of GLSL 1.5 specification few functions have been promoted to GLM core implementation: determinent and inverse (actually a GLSL 1.4 function). Some bugs have been fixed as well.
GLM development progress have been quite slow these days but I hope to give some interesting feadback about GLM 0.8.4.x very soon.
Update: GLM 0.8.3.5 is already released to fix a bug.