Maps and upgrades, pure and simple. When I bought my copy of TT6 (PPC) over two years back, TT were promising PPC users regular map updates and competitive upgrades with following versions.
Then they reneged on that promise and refused to release v7 (quoting piracy issues, for pities sake - a right slap in the face to honest users, if you ask me, as they were practically insinuating that all PPC TT users were potential software pirates), and shortly thereafter, no more map updates for v6 users either. Instead, they concentrated on PND (Personal Navigation Devices) instead (where they could make loads more money). Commercially, a not unreasonable decision, I will grant. However, the reasons they actually stated were at best spurious, and at worst grossly insulting.
Even now, bowing to pressure, they've only released PPC version 7 to retail - and that's obsolete as well, since version 8 is the current PND release, not to mention the problem that it will allegedly only run on very high-end PPCs/PDAs - their list of 'compatible' equipment is woefully short, to say the least.
That and their avoidance of interest groups and reviewers (have a look on PGPSW for more on that, or even on my blog) over the last two years, and my opinion of their board of management couldn't be much lower than wooden whale droppings on the bottom of the ocean.
The software itself is fine, if dated; the major replacement issue is in mapping, frankly.
Don't get me wrong: I LIKE the software. It's the company's treatment of it's customer base that's got me up in arms: It's at best ignorant, at worst contemptuous, of us, and I for one have had more than enough of their attitudes for one lifetime.
Therefore, I will not part with money to TomTom again. My hard-earned is going to one of their competitors instead, and I'm testing out SatNav trialware at the moment, looking for an adequate replacement.