I had an option to buy a Canon EOS 600D with 18-55 IS II Prime lens together with a Sigma Telephoto 18-250 OS This package and a bit more for $1250
and now I have purchased 2nd Hand a much bigger Sigma lens 50-500 DG HSM but not OS

F4.0 - F6.3 Got this for $800
It was advertised privately as a 150-500 lens which does have Optical Stabilisation which is what I wanted. hmmm
I paid cash at his home - country family desparate for cash, and checked it out in the camera shop - I already checked it for focus on owners 600D first. Then in the shop, I noticed the zoom range was for the Bigma lens and was then upset as it didn't have the stabilisation feature I was expecting with the alternative lens. Sighhhh.
It's cheap enough anyway and I purchased a mono-pod to place it on which will help with camera shake, which auto stabilisation nearly fixes. All for birdy shots and airplanes!! Still with a bottom range down to 50mm it will still be very usable as a single lens - except for the bulk and the weight!!
Well it is totally a new camera, so lots to learn. I still have a fairly new Olympus Stylus1 travel camera with a 28-310 lens on it and F2.8 all the way. But it has a small sensor and the Canon is 50% larger in that respect allowing me to crop much deeper and still have good detail and very little pixelation.
I need to take some pics this weekend if the weather allows!!
Graeme