thx guys, yeh the jittery-ness is because of both the camera movement and box2d, and to be honest i hadn't really noticed it, but i do now!
for the debug drawer i just hacked apart the box2d one, i basically just do an AABB query of the screen rectangle to get all the visible fixtures then use slightly hacked versions of the debug drawing routines in b2World, just copied and pasted into my own classes.
the tiles are all just separate polygon shapes, grouped into bodies of 4x4 tiles to speed up the broadphase. i'm actually super-stoked to see it running at under 2ms/frame on my comp, but i'll have to address that jitteriness, most likely just in the renderer.
hmm cegui, yeh ... you know i think I tried tgui and sfgui a while back , as well as other gui libs like gwen etc., but i think i settled on cegui mainly because it has been used successfully in commercial projects, although it is quite a beast to use, considering my gui requirements are quite low!