A cursory reading has not enlightened me.
$83,000/year to store your log files for you (you have to do the work of storing the log files).
Biggest strength is that it is user-friendly. I had very little trouble finding logs I care about, and to set up monitors + dashboards.
I've been at many companies where they roll out Datadog and collect a crap ton of metrics/logs and so forth. Teams act all gung ho about "being data driven team" but quickly learn, almost all the numbers don't matter. As SRE, I attempt to drill down but any observations are met with silence or "Oh yea, that, meh, toss another 2 cores at the problem and let's move on."
At the cost of Datadog, their cost rarely exceeds outage cost or higher cloud bill cost. If you think you need it, buy it for a year where you can probably get good discount rate, use the data to rapidly improve most glaring issues you have then cancel the contract until you need it again in 3 years.
Obviously, if you are in highly responsive business, none of this applies but for us just cranking out B2B Rest APIs, you will be fine without Datadog.