One thing about pen tool that can be kind of tricky to adjust even in 0.92 is Mass parameter, where even in that version there's not enough granularity literally just between 0, 1 and 2 (it honestly could use about a 100 levels to adjust between just 0 and 2), and the lack of granularity and pen control is made even more severe in 1.x where there's not enough granularity even between just 0 and 1, and even 1 already feels much slower than higher settings in 0.92. Though I'm not sure if fixing that would even be that pressing at all if it was just brought up to 0.92 level of performance.
I don't know if anything is solved in 1.5 dev build yet, but the calligraphy pen there seems to be even worse than before and worse than even in 1.4.4. It's frankly impressive. I take it nobody actually uses that tool for drawing at all (which would explain a lot really), otherwise the issues with it would be immediately glaring a while ago.