For a hobbyist, no. For a product that ships thousands of units per month then maybe.

You can pick up a AT91SAM7S32 chip for about £3 in one off pricing. The AT91SAM7S256 can be had for about £8. They're significantly cheaper in even low volume multiples of 100.

Dev boards are cheap too, maybe ranging between $30 and $100 depending on what goodies the chip has on-board.

Given that your development tools are free (and the C compiler actually works - gcc) and that the jtag interface consists of a 30p buffer, the cost in terms of hardware & hair loss is significantly lower than using a PIC or AVR.

I have on my desk here at work a £12,000 emulator for a siemens processor, an AVR jtag-ice and a usb jtag interface for ARM and I can safely say that any project we do here from now either uses ARM7 or xscale. It's just not worth the time/effort/money trying to coax a 8 bit c-compiler to generate code that works, even for trivial applications.