As it is next to much of Boston's finer points of interest, plus very good shopping.  It is also convenient for clients to get to.  The downside is that it is the priciest area too.

The North End and Waterfron areas are also very nice, but less convenient.

Also bear in mind that the hotel workers union is threatening to strike shortly, so you may want to hold off till that situation is settled.

Downtown Boston, Theater District is also a great place and convenient for a lot of clients who work and live in the area. The rate for the hotel may be a bit less than Copley Square. Sightseeing would be convenient as the Boston Common, Fanuel Hall, Financial and Theater District is within walking and public transportation distance.

Gemma,

It's great that you're planning to visit Boston -- long overdue, imo. Others will mention Copley Sq (aka, the Back Bay, and I agree that that's good); also think about downtown (near financial district, Chinatown, and the common), or even Cambridge (near the Charles River and Harvard Square). Seaport is up and coming, but a little harder to get to, though not impossible.

(Guys, make sure you see this "Gem"-ma when she visits -- a sweetheart of a woman and a high-octane partner in the bargain. I highly recommend.)

RM