Hi, I ended up with the 24-105/10-22 combo and like it a lot. When I finally upgraded from the 18-55 kit lens I wanted something substantially better and also some more reach. I went with the 24-105, and the year efter I got the 10-22. This is an expensive kit, but really good (in my opinion). But if the 15-85 had been out when I first was about to upgrade, I would likely have gone that way instead. Of course there are times when I wish the 24-105 wasn't limited to f/4, but you can't get it all and I've choosen longer reach.

One thing though - when you say you're about to buy your first DSLR, my recommendation would be to take it easy with the big investments. Maybe the 18-135 kit would be a good start, and when you have learned what you're missing with that lens the answer to your questions may be answered "automatically". E.g. when you have built a library of lots of photos you can easily see what focal lengths you prefer.