Exact same panels as on Samsung S8 / Note 8
Even has the stupid pentile layout... So it shouldn't have issues better or worse than those phones. The Pixel 2 uses an LG POLED instead of Samsung AMOLED, so the problems on one aren't necessarily the same as the other.
Image retention is (eventually) an issue with OLED in general, along with off angle viewing color distortion. While Samsung did a lot to mitigate it with their next gen panels that first appeared on the Note 7 (which all reviewers said had the best display they'd ever seen, though that was largely forgotten once they started catching on fire) which is probably why Apple finally decided to take the plunge with OLED.
There are tradeoffs with any display technology, I am able to see a slight color shift for off angle viewing on my X, and just checked a friend's S8 and it is the same on hers. There is zero degradation of off angle colors on my 6S plus, but that's one of the factors were IPS is superior. That's probably less important for a phone since you don't tend to use your phone at a 60* angle. Haven't seen any image retention, but I sure hope I wouldn't after three days!