Thanks all for the quick replies. Let me expand on my gear a little more.

70-200mm f4 L IS
15-85 mm f3.5-5.6
50 mm f1.8
18-55 mm (kit lense)

I find that I do 98% of my shooting outdoors. And since I live in Seattle, water tightness is a concern. Basically I love my XSI, but I don't feel comfortable taking out when it's damp.