hmm. the glass should be visible (have a look at a lightbulb anywhere, you should be able to make out its shape). Use the materials incandescene to bring it out a little. You should try to use an extruded surface as the light filament and the glow should be readable.
its a bit dark too and a little hard to tell what's going on. But the lighting on the bulb should illuminate the surrounds a lot more. I would lose the shiny table surface. There's a short film you can download if your connection is fast enough - there are 2 actually - its called BULB and BULB 2. Look for them if you can - I can't remember where I found them from but they'll be usefully to see CGI lighting could be done.