Right. I have been using the lens on a daily basis since getting it, and so far I've been extremely happy despite developing a bit of neck/shoulder trouble that now seems to have disappeared. Then today this happened:
The barrel got stuck. Well, stuck... it won't retract past 180mm or so, meaning I can't engage the zoom lock, which is a major pain when you're some 30 km from home and on a bicycle. As luck would have it, today I was usuing my Lowepro Flipside AW 400 bag rather than the laptop bag I normally use, because I was out in The Wild rather than doing urban birding... in its present state, the lens wouldn't fit the laptop bag.
Anyway, going by the feel of the jam, I think a bit of the weather sealing of the zoom barrel got loose and is now preventing the barrel from being fully retracted. I'm not looking forward to having the thing repaired, because just for fun I took out the 300mm + converter a couple of days ago and couldn't believe how extremely cumbersome that combo was compared to the new lens. Urgh, or in the words of the inimitable Jon Spencer: