I have visited Skiathos many times and I have to say its one of the most pretty, friendliest Greek Islands I have been to.
Its is only 19miles square , so quite small but has over 60 beaches .
Skiathos town is a maze of little cobbled streets and around every corner there is some boutique type shop or gem of a taverna.
There two harbours to skiathos town the old and new, the new side has very trendy clubs, which only open from July to September, they are very sophisticated and you can stay out until dawn dancing the night away! The old harbour front is lined with bars and restaurants going all the way up the cobbled steps to a square with a beautiful church as the main focal point. The cocktail bars are so nice with trendy bean bags to relax on and lanterns in the trees -very pretty.
The two harbours are lined with many boats offering trips around the islands and of course visiting all the film sites for the Mama Mia film, which was partly filmed in Skiathos and her sister island Skoplos, this is well worth doing , if only to climb those famous steps like Meryl Streep, up to the church where the views a stunning.
Linking the two harbours in the Bourtzi, it is a spilt of land into the sea, covered in pine trees like a lot of Skiathos. On the Bourtzi is the local hall, you will see people getting married, it is a meeting point for the locals and often in the evening men will be playing dominoes under the trees. At the the top there is a lovely café which serves excellent espresso and here you get stunning views of the Aegean sea and other islands.
From Skiathos town there is a great bus service which goes from the harbour to the other end of the island where some of the best beaches are to be found one being Koukanaries. The bus runs from 8 am to 2 am in high season every 20 minutes , there are 22 stops so no danger of having a long walk if you miss your stop, its not uncommon to be going in to town at night in you best clothes and people will be catching the bus in beach gear as they have been catching the late evening sun.
I say visit Skaithos and see it for yourself you will not be disappointed.