My dime, TL; DR: I like PrimeVue, but I hate the lack of community communication, lack of functionality in the components, and the oddity of supporting "old" versions. So...
1) PrimeVue still has wild bugs that can break the layout. t.co/Grm2gfDaGJ
2) In PrimeView quite simple things are not implemented. For example, the ability to programmatically open and close a menu. t.co/67VPtgd0jG
3) Complex components like AutoComplete are also lacks popular features that other frameworks / components have. t.co/bWVouD83XL
4) No releases for 2.x branch in the last month. Although this version of Vue is still mainstream right now (I think).

5) I would like a little more attention from the developers to the community. I understand that there is paid support, but I'm afraid to try it. Bad feedback to regular open source developers.
