What piece of photo gear did you think was just going to be awesome and you were sadly disappointed
Canon EOS 5Dmk2 (crappy AF, good low-light performance)
Canon EOS 7D (good AF, crappy low-light performance)
Canon EF-S 10-22mm UWA (mechanically & optically inferior to Tokina 11-16)
Canon EF-S 18-55 non IS kit poo
Canon EF 20mm/2.8 (horrible product)
Canon EF 28mm/2.8 (slow buzzsaw AF, ugly bokeh)
Canon EF 17-40mm/4L (on the 5Dmk2 this produced VERY ugly corners & the sharpness was lacking. They should drop this off the L list and drop the price to half of what it costs now)
Sigma 12-24 EX DG HSM (bad AF, randomly soft left side of the image)
Sigma 50mm/1.4 EX DG (bad AF, diffraction patterns visble @ f/1.4-f/2.0)
Sigma 70-300mm EX (slow & bad AF, bad image quality, just so awful)
Nikon AF-S 35mm/1.8DX (sluggish AF, my copy flares -> unsuitable for night photography)
Nikon AF-S 60mm/2.8 macro (vignetting @2.8 too bad, AF problems w. d300..)
Nikon AF-S 55-200mm VR f/4-5.6G ED (too slow AF for action)
Some Tamron 70-200 zooms (slllooowwww AF)
So far the experience with Nikon has been nicer than the previous years with Canon.
Not to seem like I bash every piece of equipment there is, I am currently very happy with my d300s & 12-24mm/4G DX, 85mm/1.8D, 180mm/2.8 IF-ED, 50mm/2 AIS, 135mm/2.8 AIS & Sigma 150mm EX DG APO macro. And a few old Contax Zeiss gems I have.
Canon also makes some stuff I like very much. But their current line of bodies below 1Dmk4 is too appalling for me to think about ever touching that stuff.