cw8: How much of an image loss at the 270mm end? Loss of sharpness or general IQ? Don't feel like lugging around a telephoto and my kit 18mm-135mm isn't that good for taking birds at the long end.
Your macros are crazy amazing!! How much do you spend on those macro lenses??
You'll lose sharpness and overall image quality as well - simply put its a superzoom lens so whilst it gives you a lot of convenience at a moderate price it also has to make sacrifices to achieve that. However its hard to put that into words since each person has their own budget and requirements and also their own understanding of what is sharp/soft.
Best advice I could give you is to try the lens out in a local shop and see for yourself (remember take your camera and take shots and then review on the computer, not just the LCD on the camera back). That will give you the best idea of how its performing at the long end and if its performance is enough for you.
The thing is if you want good bird photos you'll need a long telephoto lens - most bird photographers say that it starts at 400mm and I'd agree with that. Sure you can do it with shorter focal lengths if you can get closer to the birds, but many are hard to approach and small birds really are very small ;)
You might want to look at some options such as a sigma 120-400mm which would probably be the cheapest new lens moving up from the 18-270mm. From there you've then got a series of options at over double the price, such as the 300mm f4, 400mm f5.6 and 100-400mm - the cost is higher and they are larger, heavier options - but if you're serious about birds (and other wildilfe/further off subjects) then they are great options.
There are also some 70-300mm options that I would expect to give better performance over the 18-270mm which will be closer to the current budget of the 18-270mm. I can't comment much on them however as I've never really looked at that area of the market to know well what is a good recommendation - but it gives you a reference point to research and consider.
As for the macro gear the lenses vary in cost - sigma 70mm is the cheapest (and by no means a poor performer its wonderfully sharp) and then it goes up to the Canon MPE 65mm which is currently my most expensive (and stupidly difficult to use with its high magnification). Flashes however for the setup have cost almost as much as the lenses and then we have all the addon parts as well as tripods.
Suffice to say since I started photography I've not been able to upgrade my computer in a long while ;)
