Looks like I'm suffering from self-inflicted dilemma.

Or just plain curiosity...
What I have Currently:
Canon 40D. EFS 17-55mm f2.8 IS. Speedlight 580EX II. EF 70-200mm f4L.
What I'm Being Tempted to Switch To:
Canon 40D. EF 24-105mm f4L IS. Speedlight 580EX II. EF 70-200mm f4L.
What I Shoot:
- Group photos. Some portraits. Landscapes.
- I'd say 50% of the time, I am/will be shooting indoors
- Occasional night shots (usually with tripod)
I'm generally happy/satisfied with my 17-55mm f2.8 IS lens but find it quite cumbersome to change lenses for tele shots. Apart from that, I'm also finding 55mm to be on the short end in several instances. Having used a friend's 28-135mm lens before, I'm sure the 24mm end of the 24-105mm won't be an issue for me.
From the looks of it, I guess what I really am looking for is a good walkaround lens. That's why I am considering the 24-105mm as replacement for the 17-55mm. Question is, is it really worth spending the money for?
:Later,