igor_masluk

David, I believe you can leave you camera on all the time - the camera will go into "sleep mode" (power down) after a few min of inactivity - don't remember exact value - and will wake-up once you depress shutter release or review button. The power switch and the quick control dial lock are combined to a single switch so when switch is in "ON" position camera is powered but quick control dial is locked (preventing user from accidentally changing exposure compensation, etc.,) and next "ON" position marked with white marker pointing to quick control dial will unlock it.

 

Igor.

For the kind of photography you're doing Speedlight will do the job - if you have relatively low white ceilings just add a Stofen diffuser to your 550, point it up and you'll be amazed with results. At least I was - a $16 (still overpriced though) attachment produced results almost as good as my studio strobes.

If you absolutely have to have Canon lens and price is not concern - go with 2.8 IS - otherwise you may find that you'll need tripod more often then you expected. I struggled with the same decision - ended up with Sigma 70-200 2.8 ($535 new) - fast, sharp - no complaints whatsoever.