My verdict: the historic tool that has had its day.
Reply.io remains powerful and complete, but newcomers are more agile and cheaper. It's a very powerful historic tool that offers many possibilities (multichannel, AI, etc.). But honestly, I find the tool has become a bit outdated compared to newcomers (Instantly, Smartlead) who are more agile and focused. It's still a big machine, but it feels a bit dated compared to the new wave.
What I like less: the aging UX, the high pricing for what it is, and the general feeling of heaviness. Newer tools often do better for less.
My advice: if you're already on Reply.io and it works, stay there. Otherwise, look at Instantly for simple cold email or Smartlead if you're an agency. Reply.io is no longer the default choice it used to be.