| Really depends on what department you go into. I'm an MCB major, so I'll share my insight from the hard science end:
The lower div science and math classes here are large and impersonal. Some profs are only teaching because the university is making them, which means that they won't be very good teachers; others are voluntarily teaching, which means that they'll be pretty good. But true, Berkeley is more a research institution than an educational one, which is why the school pours money and care into the grad students and kinda kicks the undergrads to the side. But again, that's only speaking from the science point of view. The upper div science classes tend to be a little better - classes are smaller; classes are no longer geared towards weeding students out and faculty teaching quality improves as a result.
One major reason why the university puts so much care into its grad students is because they teach so many of the classes here, and it's a necessary form of quality control. Sure, some GSIs slip through the cracks once in a while and turn out to be terrible teachers, but the same goes for professors. The quality of education here, as in many other large, prestigious schools, is based on a trickle-down effect through the hierarchy. Perhaps not the best form of education if you're looking for a personable experience, but considering that the large public schools are basically "degree mills" that simply churn out degrees, it works for their purposes. For a more personable, intimate undergrad experience, schools like Princeton and the liberal arts college (minimal or no graduate program, all attention is on undergrads) might be better suited.
I've had a very, very positive experience in ALL of my humanities courses, especially with the music department here - I haven't had a bad music teacher yet. The music dept. isn't the most renowned or top ranks, sure, but the quality of teaching is really, really good - the dept. is extremely small so the faculty are very personable and friendly; class sizes are really good (20:1 or less).
So it's impossible to generalize the ENTIRE undergrad experience as one way or another - it really varies depending on what sector of the undergrad education you're looking in. But it's still absolutely a great place to go for grad school - tops in the nation in damn near everything, baby. | 
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