There are a lot of Boston Tailor threads, so I am not going to start a new one. A great, old school tailor has recently relocated to Brookline. Brookline Tailoring Plus - 3 Kendall Street, just off Cypress, behind Kirkman's Market.
The owner/operator is Mark Aroush, who sold his shop in Cambridge (Aroush's Tailoring - 864 Mass Ave) about two years ago. I believe that shop has changed hands a couple of times since.
Mark is a true old-school tailor who wants to keep busy and did not enjoy sitting around in retirement. He has a great eye for all aspects of men's and women's tailoring. He has done alterations work on three suits and several pairs of pants for me, and I have no complaints. I used to use Mario the Tailor in Chestnut Hill, but Mark at Brookline Tailoring Plus is MUCH better. For top notch work, this is worth the trip.