The 70-300 lense you mention is probably the same one that I have.
It is quite a versatile lense, the macro function isn't too bad BUT you need to have the lense zoomed right out so handheld shots are not really an option. It's taken me a fair time to learn that I just cannot really hand hold this lens so a tripod is pretty much a requirement too. I tend to use it for the 300mm end than anything else.
I think I paid around £180 for mine last year. I am fairly happy with it, really it's my technique that lets me down if anything so if you do go for one, remember that it takes practice - it's not the same as just hand shooting with a shorter lens.
This shot was taken with it not long after I got my camera and to be honest was more luck then judgement at the time
