Love the pics too. I am wondering if one of the first things you noticed was the accuracy of the Oly colour? With my floral photography it still impresses me as to just how accurate the colours are.
I have the 75-300mm. Use it all the time for birding. It is as slow as a wet week, but that has never worried me for as long as you have plenty of light it gives good results and the cropping factor is tops. On a dull day it stays at home.