I transited through Skiathos in September 2012 and June 2013 - both times on route to Alonissos. The first thing you'll notice about Skiathos is the airport runway. Or, rather, the lack of it. One of the shortest commercial runways in Europe -with sea at either end- you're in for a quick landing. Expect vigorous braking, wing flaps fully down and jet engines roaring in reverse thrust (or combinations of these) before rapidly reaching the turning circle at the end of the runway. I must admit I loved it but can see that for nervous flyers it won't compare favourably to the sedate trundle when landing at Gatwick. Likewise, expect take offs to be fast and steep. Larger planes take off with limited amounts of fuel on board to keep the weight down and then make the short trip to the mainland (in my case Volos) to be fully fuelled.
One of the local landmarks is the church of Agios Nikolaos and its stone clocktower. This stands high up above Skiathos Town and can be seen from the harbour front. Just work your way up a series of narrow steps and alleys until you get there (there are some signposts here and there to help). What you get from Agios Nikolaos is a panoramic view over the town and harbour and it is well worth the few minutes it takes to get up there.
Aviation enthusiasts can stay on the harbour front and watch/photograph the planes coming in to land. In fact, Skiathos is a bit of a magnet for plane spotters due to the public road right at the end of the runway where planes pass low overhead. You can also expect to be waved at when taxiing before take off!
Certainly, from my limited time on Skiathos (and only in Skiathos Town) it certainly feels bigger and busier than the other Sporades islands with a plethora of tavernas and shops and even an open air cinema showing, inevitably, Mamma Mia! Regards, David.