I remember when I got my first set of hole saws. They looked like this:http://www.boschtools.com/Products/Accessories/Pages/BoschAccessoryDetail.aspx?pid=537#specs
Little did I know I was just beginning a long relationship with hole saws. The larger ones, in particular, seemed to be good for only a very few holes before they lost their bite and stopped cutting and started smoking. Especially when doing service changes, the slightest contact with asphalt roof shingles - either side- seemed to spell instant death to the teeth.
Well, I recently had the need to try this new style saw:http://www.boschtools.com/Products/Accessories/Pages/BoschAccessoryDetail.aspx?pid=456#specs
It is expensive. It will NOT fit your existing arbor. It does NOT come in the exact same sizes as the ones in the usual electricians' set. Yet, for cutting through solid wood siding, a layer of tar paper, and a layer of OSB, it simply raced through. The hole was very clean, and showed no sign of gumming up from the tar paper.
I recommend replacing the conventional saws in your kit.