[redsnapper]

Some advice please!

I'm about to head off to South East Asia for a month and want to make the most of the photo opportunities while I'm there. I'll be taking the following:

Canon 40D
Sigma 10-20mm wide angle lens
Canon 50mm F/1.8 EF prime
Canon 28-135mm EF zoom.

Here's my question - I've been eyeing up a canon 24-105mm L lens for years, and if I'm ever going to get it, what better time than now? But... is it worth it, or will my 28-135mm do just as well? How much of a difference can I expect to see in image quality, focusing speed and accuracy etc etc? (I currently find my 28-135 often struggles to produce pin sharp images).

Any thoughts gratefully received, anyway.