Here's one thing to think about...
If you're using a 628 on the TX end, and a 628 on the RX, and you're running them off the same crystal, using the same divisors for the baud rate generator, it won't matter how far off you are because both ends will be off by the same amount in the same direction.
And serial ports (whether it's on a PIC or a PC) can generally tolerate being off the specified buad rate by a few percent either way.
(also, baud doesn't necessarily equate to bits per second...although that's generally the way it's usually thought of)