It's a surprisingly good game with mechanics that are well thought off.
The only negative thing I noticed is that, when filling up the level mid-scoring, the scoring of the lines ends immediately in favor of deleting lines. This actually ruined my very first Pentis as the game made it count as a Triple due to said level-up. My second Pentis was "true" though so that felt nice.
tl;dr: Make the game finish scoring before removing lines, then the game is perfect as far as I'm concerned.