Ken can take quite a beating in the web-photo world, and very-true that he is "very confident" in his writings. He admits that...so take his writings with a grain of salt. good info, none-the-less.
I think if you want one lens to do just about anything...the 18-200 is a VERY nice lens. That being said I'm starting to take lots of pictures and different types of photographs. so....I, too, am going in the direction of "fast" lenses. My current faves are my 85 and 50mm 1.8's they rock....but are fixed focal length, so I need to use my "sneaker zoom" (walk back and forth).
I would also recommend Nikkor Glass...it's just plain great. spendy, but great. We drive Cruisers...not because they are cheap to get or to work on...they are just great.
If you want to go shoot something soon without spending lots of money. go get a "nifty fifty". that is, for like $130 you can get a 50mm/1.8 Nikkor lens. the sharpness and low-light capabilities will blow you away. and it's cheap.
Here are some shots taken in a VERY dark bar (jonesy's): http://www.flickr.com/photos/2287049...7614180773065/
The aftermarket lenses that get good reviews (so I've heard anyway) are:
Super-wide angle (no fisheye): Tokina
11-16mm f/2.8 AT-X 116 Pro DX Autofocus Lens for Nikon Digital
Telephoto 100mm f/2.8 AT-X M100 AF Pro D Macro Autofocus Lens for Nikon AF-D
NiKON Big-money, fast, pro lens: NikonUSA Zoom Super Wide Angle AF 17-55mm f/2.8G ED-IF AF-S DX Zoom-Nikkor Autofocus Lens for Digital Cameras