Unno, I learned my lesson and only buy Nikon glass.
Even the cheap 55mm-200mm plastic-case lens is nigh amazing. I got a shot of 2 trees on an “island” in the middle of a small lake (or large pond), an egret tucked in the middle between them (’though I think on the other side of the lake, just framed by the trees), and on my first camera, a lowly D3000, it came out so clear that when you’d look at the 100%-crop image (ie, pixel level), not only could you see the egret’s eyes, but his pupils, clear and absolutely in focus.
Love him or hate him, but Ken Rockwell loves that lens as an amazing featherweight zoomie, and he’s 100% right.
Granted, I haven’t touched that lens in a decade or so since I got my 28mm-300mm donk, but I haven’t had the heart to sell it off or anything.
If you just want crappy pix for posting on the web or something, aftermarket lenses can be fine. If you want awesome, though, stick with OEM (Nikon, Canon, etc.).
I still want a Noct, though.