He also had about the same or more invested in IBM. He's a great investor but not infallible.

Yes, but he sold 30% of IBM at around $180ish for what I assume is a nice hefty profit.

His cost basis was $170 [1]. It's a modest profit as a percentage, and he's now close to underwater on his entire investment into IBM due to the drop (the ~$2 billion in dividends he has yielded, may keep him over break-even, unless IBM plunges again).

[1] https://www.cnbc.com/2017/01/19/warren-buffetts-ibm-stake-wa...

Pretty sure he's not losing sleep over where IBM is today.

If he still owns it, he's still bullish on it.

The stock already had a lot of growth expectations priced in, so whether he got it right from today's pov depends on whether these growth numbers are better than his buying price implied.