Very easy to use and compresses ok

Disclaimer: I’m rating this with Imagify version 1.4.6

First the good.
Fantastic integration with WP. Ease of use is outstanding. Very fast and convenient.
For a small site/blog the free tier will probably be enough on a monthly basis. For larger sites their paid plans are pretty decent price-wise.
Great comparison tool to see difference between compressed and original.

Then the bad.
Compression. This is the reason why I’m giving it 4 stars. (I use the ULTRA compression setting always and mostly use JPG files)
On certain images Imagify returns a result that my file is already compressed and does nothing. On a same file when I use one of my other tools for compression (JPEGmini), I get additional compression by sometimes 50% or more.
Once they improve their compression algorithm, I’ll be a happy camper and migrate fully to them. Until then, it is a useful tool alongside other compression products.