Just returned last night from a week long trip to Skiathos. Just wanted to warn you to be prepared to open the old wallet. It's a beautiful island with gorgeous beaches, but don't expect the low prices you might expect to find on other Greek islands. Also don't expect the people to be as nice either. We have travelled to other islands and found the Greeks to be very open and warm people. Sorry to say we did not have the same experience here.
I would definitely recommend this destination as one that would offer the opportunity to just chill and relax, but cannot say that I will ever return.