I have the 24-105 F4L USM; I would say it is probably one of Canon's best walk around lenses- its sharpness will amaze you !

Either, both have a warranty !

The top shot is a Nuthatch, not sure about the lower one though !

I think they are pretty good; perhaps a higher shutter speed, but i think most shooters would have been fairly satisfied ! I have seen a LOT worse, where the shooter thought they were the bees knees- just keep shooting, there's nothing wrong.

Hi, I have been in photography almost 60years! I have to say, that with everything advised by the mags to use RAW, in actual fact, you will be far better of using JPEG until you are familiar with the way everything works. For one thing, RAW takes a lot more space on your hard disc, and processing power.
Actually, JPEG is pretty good- I use it all the time. Hope this helps somewhat.