A bit of context: two years ago I joined an undergraduate program in electroacoustic music composition at the Université de Montréal. Fortunately the faculty has decided to use mostly free software in the classes. They recently moved from Max/MSP to Pure Data to teach algorithmic composition. OpenMusic has been used for computer assisted composition classes. On acoustics classes, Sonic Visualiser is the recommended tool. For everything related to audio processing and sound synthesis we mainly use Python pyo library and Cecilia, both developed by the professor himself. Other many free softwares are used for building digital musical instruments in the courses: Arduino, SuperCollider, OpenCV, openFrameworks etc.
So far I touched two proprietary softwares for my classes. First it was Reaper, a sequencer which has been recently adopted in replacement of Pro Tools in some grades. Reaper has a less unfair distribution model compared to Pro Tools and despite being a closed piece of software it somewhat looks like a community-oriented project, being developed by a small team of free software enthusiasts. Being an amazing, complete and still lightweight DAW I hope it goes free some day in the future (I've read about this possibility somewhere in a forum that I can't find now). Anyway, after some months playing with Reaper I went back to Ardour. Because it's free, not because it's better (Reapper still seems unbeatable here).
The other was Finale, an alternative to MuseScore for music notation. I used it for three compositions mainly due to its playback capabilities. As a middle-aged music student I don't have the internal ear enough developed to listen orchestral textures, articulations and other details provided by expensive VST stuff. However, I found editing with Finale a pain in the ass. It's so bugged that I thought I were using a sort of alpha version. Basic editing is much more logical and elegant with MuseScore. After all, these first experiences with Finale didn't convince me that such realistic playbacks are adding any value to my music. I suspect that moving back to soundfonts or even composing with no playback at all will probably force me to exercice more critical/analytical listening whenever I need to understand the effects of a specific instrumental gesture and instrument combinations. So, I'm back to MuseScore. Not only because it's free, but also because it's better (at least for my current needs).
MuseScore has allowed me to easily edit music scores in a free operating system, using a small and not so powerful laptop. Unable to donate money to this amazing project I've been happily giving some time to it, by testing new releases, reporting issues, translating to portuguese and making available unofficial Debian packages while the current maintainer prepares the official one, which seems to be coming very soon. If you're a Finale/Sibelius user and don't strictly need that universe of orchestral VSTs samples for your music work, please give MuseScore a try. Have a quick look at its online handbook and in a few minutes you will be able to experience the real pleasure of music scoring using a computer. You can try different soundfonts, including the so nice Sonatina Symphonic Orchestra.
Below is a screenshot of MuseScore 2.0, which will be released very soon. You can download the RC version for your system in the MuseScore website.