I'm a relative newbie to Turkey, but I will say, that having visited
Icmeler for the first time last year, I'm hooked.
My only trouble is, despite planning to go this september, I can't afford to get back there until 2011.
As for anywhere else. We found Kusadasi had much more history, both in the town and with Ephesus less than 10 miles away, ideal for those looking for good sightseeing.
But beware. Kusadasi is a cruise destination, so prices reflect that when the liners are in (sometimes double for everything) and we found it generally dearer than Icmeler too. And nowhere near as friendly.
There is a large Dutch

and Russian

influence in Kusadasi too.
Icmeler is by far the best of the little of Turkey that we've seen. And we have friends who have experienced the same feelings as us.
Cheers
Andy