Guitar Pro

Using the tab/instrument view is really useful to notate the tones of your guitar into a tab/sheet music, and the compatibility with many other strings instruments(Ukulele, Bass, banjo) make it easier to transport your ideas to other players, even if they are really far from you.
The printing options are awesome too, if you can't afford a printer, you just export your tab/sheet score into pdf format and then can send it to any place so they can print your parts or chord charts.
Also, the playback/loop option is EXTREMELY helpful whenever you encounter a hard to learn, it allows you to go from really slow to the exact tempo you are looking for, so, for practicing your instrument is a really awesome tool.

There are a few things that can be improved, for example, if you happen to be a producer or an orchestra/band composer, guitar pro will limit you the way you write your music, it does not have a natural flow when it comes to transport instruments(say, many of the brass and woodwind family) so, it might get confusing whenever you have to write something for a trumpet or alto sax player.
Also, the playback or RSE (real sound engine, which is basically an emulation of a live instrument) is not that good enough, compared to other software that is around nowadays, most of the time I prefer to use the midi default playback, because it can get too noisy and unproportioned.

About the software functionality: It was and has become even more user friendly to write, edit and play music scores. Not only that: it includes a Chords library that you can use in every single instrument (mainly focused on guitar, adding at the beginning of the score all the chords used). You can make it as simple as you want: tablature, chart or pentagram...or why not, all of them! It includes a great library of RSE instruments that will help you imagine what your music sounds like. Export your score as midi and use it on your recording software on VST instruments. And it's absolutely affordable!
About the customer service: Few years after I started using it at home I started to write music for my church which doesn't have a lot of money to spend on very specific software like this. However, we needed more than one license so we contacted them. Their interest truly was to help us and yeah, completely helped us to get exactly what we needed. Best people on Earth!

It might rarely crash but it has been improved a lot with the years and updates. Just keep saving all the time as you should with any software you use and you'll be fine. Also the RSE sounds for winds are not good, they're just to give an idea. The interpretation of dynamics is weird mostly when changes are extreme but again, it's not designed to sound like a VST.