Given some cash to put into the market, it seems like now might not be a great time to add to BRK. Thoughts?

Depends on your hold period.
If you're looking at holding the position more than a couple/few years, it doesn't make a whole lot of difference.
It's not as if the stock is wildly overvalued, it's just a little above the modern average.

My various models currently expect returns mostly in the range inflation-3.9% to inflation+4.0% in the next year, median inflation+1.0%. One optimistic outlier expects inflation + 7.0% (bases simply on P/B and price since 2003).
Those aren't awe inspiring short term numbers, so if you'd like something with high odds of looking very good within a year, Berkshire might not be your best short term horse for the race.

The reason for the wide range, and the substantial pessimism of some of them:
Some models use book, some use my value metric, some use a mix of the two.
My value metric is quite a bit more conservative than book at the moment, as it values Apple based on a multiple of earnings rather than current market value.

Jim