It is noteworthy that Robin Van Persie is the one welcoming him to the club. The two players have a picture together and they do not seem like they were swapping plans for an evening out. RVP may remember this from the Amsterdam Cup which Arsenal won beating Ajax, 1-0 through his 87th minute goal.
So RVP should be the first one to appreciate the simple minded steel that Vermaelen brings to the squad. As Ajax captain he is comfortable in a leadership role. A feature which Arsenal lacks in the back and Gallas was unable to provide consistently. A take charge personality would be much appreciated when the going gets tough.
He is known for speedy and tough tackling, at times living on the edge with his two footed stuff. Not surprisingly, he is consistently one of the most carded Ajax defenders. He finished with 9 yellow cards and a red. How this plays out in the more physical Premier League will be interesting.
He also gets high marks as a decent set piece threat scoring 5 goals this season.
As a centre back, he is ranked behind Groningen's Andreas Granqvist, FC Twente's Peter Wisgerhof, and PSV's Dirk Marcellis, putting him in the top five in the Dutch League.
There are question marks as to durability. This was his first complete season. The last two seasons he completed about half his appearances due to injuries sustained to his right knee. A gimpy defender would be the last thing Arsenal needs, a familiar story replayed many times over.