A whole, whole bunch depends on how you shoot and how hard you are on gear. The consumer lenses are mostly not as tough as the pro versions, but that is not an issue if you're easy on gear and if the individual consumer lens meets your quality needs. Between my wife and I we have three of the 24-120VRs and could probably justify a 4th since we're each using multiple bodies. That's a reflection of the usefulness of the focal range, but for toughness reasons we'd replace them in a heartbeat with a pro version if one came available.
I used to think the 17-35 was my next favorite lens, but it became a dust collector when I got the Nikkor 12-24. My wife kept borrowing it, and based on reco's from other pros I got her the Sigma 10-20. I now borrow her Sigma rather than using the Nikkor whenever I can, even if the lens cost half the Nikkor. The wide end is so immensely useful at times, and the 10 is significantly wider than the 12 on the Nikkor. The Sigma is also noticeably more contrasty and "snappy" than the Nikkor.
In your shoes I'd confer with the stock agencies to make sure that the files from your D80 are acceptably large for the broad range of needs. If so, fire away. If not, then long term a move to something like the D300 might be in order. I haven't handled it, but am impressed with what I've heard about features and image quality, so if larger files were indicated it might be an opportunity to make your job a little easier.