For a character builder, I'm finding it to be really helpful. As a GM, I manage hundreds of characters. This tool gives me the ability to create them fast and efficiently, and to get as much detail or as little detail as I could ever need. If I was a player, I'd consider the tool simply for creation and tracking purposes. In-combat ammunition tracking alone is worthwhile. However, if I was only tracking one character (even with the ammunition tracking, journal, karma and nuyen tracking, etc.) it might be a little out of my price-to-benefit range. I'm encouraging my players to pick it up though, because lord knows I don't need more characters to track. 
Also, as the future books come out, and character creation becomes more complex, it becomes a life-saver for Chargen,
as it lets you keep track effectively of all the options you are using, and make adjustments as you need to as you go without
having to completely recalculate from the beginning.(It also auto-optimizes karma spent in chargen for you. So, while you
might pay the karma to raise a skill from 4 to 5, it goes 'OK..spend a skill point to raise that skill, and pay Karma to cover
this thing you have at skill 1 or 2')