Because you said you are into IT, you might want to take a look at taskwarrior. It is an command line tool which can sync across different machines. Unfortunately, there are no mobile clients at this point.
I prefer taskwarrior because its FLOSS and answers the question "what to do next on project X?" quite well. It also performs well with my personal stlye of GTD (I implement only a few practices of GTD), and in my understanding you can do the whole nine yards of GTD with it.
The tutorial will teach you enough to make good use of the tool in about 30 minutes.
other pros: all the data is stored in plain text; you don't have to give away your data to another party.