To Refi or no to Refi

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I'd like some help thinking about whether or not to refinance the loan on an investment duplex. Here are the details:

Currently owe $139,000 with loan at 5.625% 30 year fixed. Have only owned the property for 1 year. 

I have been quoted a 3.25% with half a point on a 15 year fixed. My payment would increase by about $170 and there would be $2500 in closing costs so with the half point ($695), $3200 to obtain the loan.

Other relevant info: The rents would cover the $170 increase, but even if they wouldn't, I can afford the increase. 

I feel like if I'm running #'s correctly, then after just 1 year, I'd have paid down the balance an extra $5500+ which more than covers the loan costs and increased payment. From then on, I would only be increasing my equity at a much greater rate, making me think I should go for it.

Am I missing things in looking at this? For example, how does tax savings come into play? Any input would be appreciated.