I personally do not believe the Abhidhamma to be the Buddha's teachings, and I have my suspicions that it may in fact paint the wrong picture and be a stumbling block.
But some people believe it to the word of the Buddha, and some people take great value from it. It's not a necessary thing to learn, you're not missing out on anything great by not knowing about it, but for those of an intellectual inclination it can help them understand the mahaviharan doctrine in all it's intricacies. Perhaps some might say it has helped their meditation too? I don't know.
I'm not a fan, but I won't rubbish those who are
"For a disciple who has conviction in the Teacher's message & lives to penetrate it, what accords with the Dhamma is this:
'The Blessed One is the Teacher, I am a disciple. He is the one who knows, not I." -