For quite a while, I've been using MuseScore for the various things I need to do in modern notation (including stemless MN).
I've never used Finale or any other paid music typesetting software, but I've been very satisfied with MuseScore. Yes, it allows stemless notation.
It includes most major features I've found, including multiple voices in one staff, synthesized playback of your score, native exporting to many formats, including PDF and MIDI, and splitting a full score into instrumental parts, to name a few. The only feature I've found lacking is dashed slurs, though I wouldn't be surprised if it is added in a later release. They can easily be added later if you have Photoshop or GIMP or something.
Even if you just use it for typesetting music for your Mass programs, like I do for the occasional program I create.
Also, may I mention not only is it free, but also open source.
I've attached a Word Document turned PDF with a few things I've typeset using MuseScore to show you how well it works.
The really glaring thing about these samples in that the staff lines are not uniform; some seem wider and lighter, and their spacing is subtly irregular. And the slurs are a bit funky. But it's clear and serviceable, and worth more than you paid for it.
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