I lived in Cambridge for about 6 years from ~2004–2011. Nothing but positive experiences with Boston-area cabs. The drivers were uniformly friendly and competent, and had no trouble with the ridiculously convoluted MA street layouts. When I was carrying suitcases or moving boxes of books around, they were patient and helpful with loading/unloading. When I left my wallet one time, the driver called me as soon as he found it and promptly returned it.

Maybe you just got unlucky? Or maybe things have deteriorated since other transportation started undercutting them?

Yay for anecdotal evidence, right?