Hi,
I have the 18-200 OS which I think is the same apart from the extra 50mm.Its a great walkabout lens and feels well made...only let down is not great in low light...but VERY handy range The 18-250 should be even better!
Yea looks like the OS system may be improved on th 18-250. The tamron 18-270 vc does get some good write ups ..in fact won the best superzoom category in one of the photo mags recently,so maybe worth checking out!