I've gone through a few manufacturers, but I'm basically sticking with the LPC1xxx chips. Mostly the LPC1313 (Cortex-M3) and LPC1114 (Cortex-M0). Unfortunately you need to go up to the LPC17xx devices to be able to use regular JTAG. I don't know what there is for SWD options out there right now, but I'm using an SWD adapter from Rowley on my Olimex AMR-USB-TINY JTAG. I think finding a decent SWD programmer will be the hardest.
The M3 and M0 parts are nice. Fast, 100Mhz, 72Mhz, and 50Mhz. Cheap for the LPC13xx and LPC11xx parts, down to $2 for 8k LPC11xx parts from NA suppliers. The LPC17xx are the 100Mhz do it all parts with all the crazy peripherals like Ethernet and they get close to ARM7 prices $6 to $12 for NA distributors.
Simpler to program, the peripherals, at least on the SAM7 chips I used were crazy. My SPI library was nutty. The cortex chips are meant to be simpler and the LPC13xx CM3 and LPC11xx CM0 have compatible peripherals mostly, so I don't have different libraries for both.
Simpler hardware. Just power and a crystal oscillator. No external PLL or need to power the VCORE yourself. I can actually put one on a single sided board with a minimum of jumpers. The SWD connector is a much smaller connector, though I think I'll be moving from the standard header to a 4 pin header. The little SWD connector are expensive and I really don't need them.