If you use TomTom Home you should get software (i.e. operating system) updates for free. It's the updated maps you have to pay for. The other annoyance (certainly used to be) was that you could only register one device against each email address.
I now use the TomTom app on iPhone. It does everything a standalone does at about £35 with free map updates for life, and it plays via bluetooth through the car stereo (if required), and it travels with me wherever I am, and you can have it on multiple iOS devices, and.....