Ive been playing piano for over 7 years, and I'm going to tell you something: If you want to be decent, think that your going to need years for that. But hey, you can learn a few chords in minutes, and you'll be able to input each voice at a time.
I reckon making something simple should be easy once you get around with using the program.
Thing about this is that these programs tend to "always have something more to know about". It's like photoshop, you could try to learn all about it, but I think the best way would be just mucking about, a few tutorials and you'll learn by simply using it. It depends on how much time you want to spend really.
And about making music, its the same with piano, it all depends on where you want to go.
Why don't you actually try to narrow your search down, apart from the money you want to spend:
What about the type of key or the ammount of keys you want?