Quote:What I have: D90, 35/1.8 (DX), 18-70 (DX), 105/2.8VR, 180/2.8, SB-800.
And IMO that's an excellent set-up. Why pay a premium for getting the same at a higher price? The difference between f/1.8 and f/1.4 is 2/3 stop.
Nevertheless I see some holes in your line-up, so here's some suggestions if you want to dabble into other areas.
You have a lot of good lenses, but you're probably missing something wider, like the 24mm f/1.8 (rational choice) or the 24mm f/1.4 (emotional choice). That's 36mm on your D90 and that's close to the perfect focal length (in my opinion). I have the 35mm 1.8 for myself and unfortunately it's a little bit too narrow most of the time. I feel the need to go back to my Tammy 17-50 2.8 a lot of times.
Which takes me to the next item: You don't have a faster standard zoom. Don't know how the 18-70 is used, but there's the Tamron 17-50 (VC variant isn't worth it IMO) or the Nikon 17-55. There's also Sigma and Tokina, but I haven't been considering them. The Sigma 17-70 f/2.8-4.0 seems the other interesting choice. Of course the Nikon thing is big and bulky and the Tammy is nice and small and it's certainly one of my main lenses. I do have some issues with it, but I get the shots I want.
Next you don't have the Sigma 50-150 f/2.8 HSM II. Probably you haven't heard of it, it's a paint that such a gem is so unknown! The 50-150 is an absolutely amazing lens and built totally for DX, which means small, light and still excellent quality. Just look at the guys with the huge 70-200 f/2.8. The Sigma's the same thing only much smaller and much lighter. I love the inner zoom mechanism so the lens stays the same size all the time and the AF is quiet. Also it's razor sharp at 50mm 2.8 and at 150mm at 4.0. I bought it for 600â‚¬. If you like to be more flexible with the portraits you take, this is one lens that you must have! It's a shame Nikon doesn't have a similar option, but then it would certainly cost way more than 1000â‚¬ and I'm not buying it at that price.
You're still missing the classic of all lenses the 50mm f/1.8 or you may want the new 1.4 version. I heard the Sigma should be even better (but also bulkier). There's times when a 50mm is just right. I like to do portraits with the 50mm f/1.8, they come out with nice colors, contrast and sharpness. DOF is pretty thin below f/2.8 though. You also don't have a real head and shoulder portrait lens like the 85mm f/1.8. There's even the 85mm f/1.4. With these you should be getting some really shallow DOF shots (which IMO is just effect, but to each his own).
You may consider adding an UWA at some point. Great for landscapes. I have the Sigma 10-20 f/4-5.6 which is probably still the best wide-angle around. 10mm is absolutely fantastic. I had a lot of fun with it, also close-up. Then I left for the normal ranges again, but keep coming back more and more. Also the 10-20 is relatively moderate in size and weight. Most of the time I'm switching between choosing the 10-20 or the 50-150 along with the 17-50 which is always with me. And usually there's one prime also going with me which is either the 50mm or the 35mm.
Unfortunately I can't give much advice in the tele department. I'm still looking and evaluating my choices. I also don't have an immediate need, but need something for the next trip to the zoo. The Nikon 80-400 is pretty expensive and also not that overwhelming. There's also the rumor of a successor. The Sigma 120-400 was on my list for some time, but there's the AF issue and a colleague wasn't too happy with his (mainly because he didn't get it for a long time due to AF problems, the pictures looked good though). I don't quite trust the Sigma 50-500 or Sigma 150-500 although they're extremely tempting. I also looked at the Sigma 100-300 f/4, but while it looks optically sound it doesn't have stabilization and also 300mm isn't really that much. With the D80 I was also turned away of apertures such as f/6.3 at tele which also requires higher shutter speeds and thus higher ISO settings. Now that I have the D7000 that's no problem anymore. Currently the best option is probably one of the 500mm Sigmas.