Loved JC2 (my most played game of the past 10 years) and really enjoyed JC3 too but it didn't feel as varied to me as JC2 did.
Pre-ordered JC4 for my birthday a couple of weeks ago and had a couple of hours play on it last night. Definitely feels like a polished JC3 so far - basically the same but with some nice added bells and whistles (tether balloons are fun so far). Haven't had any crashes or issues beyond nasty looking shimmering on Rico's hair in cut scenes, but as I said I've only got a couple of hours in.
Pretty much agree with reviews - how you feel about JC3 will be how you feel about JC4 as the game's very similar, which is fine with me!