My son is graduating next week with a Bachelor's degree in bioengineering. I would have suggested that he go on for a Master's, except that he got a job offer with a prominent company in his field that will contribute substantially to tuition for grad school. At that point, and in these financial conditions, he agreed that he should take the job and pursue the Master's while there.
Personally, I went immediately from undergrad (physics/math) to a master's program (CS/EE) both to dig a little deeper and to optimize my chances at Member of Technical Staff jobs with my then ideal employers, Bell Labs and Hewlett-Packard. Got offers from both!