new lens, but which one.....

does anyone have experience with the nikon AF-S VR DX Zoom-Nikkor 18-200 mm 1:3,5-5,6G IF-ED lens? it seems to be a nice allround lens with image stabilisation....i read a lot about it in various blogs etc. but would appreciate first hand experience from somebody.... other lenses on my mind: - sigma ::: 18-50mm F2.8 EX DC MAKRO - nikon AF-S DX Zoom-Nikkor 17-55 mm 1:2,8G IF-ED (very expensive) i own the sigma 10-20mm as my only lens at the moment and i'm quite happy with it. i wonder if the the nikon 17-55 is considerably better than the sigma. if anyone owns any of these, please comment..... thanks in advance, blau