I should elaborate. I use a 17-55 on my 60D and 7D. I also have both the 24-70 f2.8L II and the 24-104 f4L IS for my 5D3. Of these three lenses, I still think the 17-55 is the best choice for the crop bodies in part for the focal range and partly for the IS with the faster aperture. As long as I hang on to a crop body, I'll hang on to this lens.
With a 7D2, I assume sports would be a subject matter. The 17-55 is fantastic with sports. I often used it to shoot volleyball from net-side where it was necessary to quickly aim at a player, focus, and shoot. The 17-55 locked on without issue. I think part of this is due to the faster lenses. Even with the two L lenses on the 5D3, the 24-105 sometimes misses where the 24-70 doesn't. If indoor sports is a concern, the 17-55 will not only help in low light, but the faster lens will make better use of your AF system on the 7D2.
That said, the 15-85 is the only other EF-S lens in this range that can touch the 17-55 for image quality.
As for the dust issue. Put a good clear filter on the lens and it isn't an issue. I use Hoya HD filters. If using Hoya, only use the HD or their new high end filters. B+W is another fine filter to consider.
Apparently early versions of the 17-55 had IS issues. I think those have long been resolved.
There is one quirk of this lens. When you zoom from wide to tele, you will feel extra resistance around the 24mm mark. This is normal. To be quite candid, this is most noticeable when you are playing with the lens and trying to figure out if you have a "good copy". Don't worry about it. I don't notice it when I shoot with the lens.
Check out Canon rebates. One may be ending tomorrow (Feb 28). I don't know if it covers this lens. Also consider Canon's refurb store. Often good prices and the lenses are thoroughly checked out by Canon (more so than new lenses off the line).
For what it's worth, my Dynamic Duo lenses for crop are the 17-55 f2.8 and the 70-200 f2.8L IS II. For FF, its the 24-70 f2.8L II and the 70-200 f2.8L IS II. Regardless the body, the 70-200 is my most used lens (for sports, events, candids, and portraits).
I hope this helps.