Andy,
I'm doing 3 designs in the very same time. Two of them have a Cygnal F001 part and I'm happy with Cygnal.
The second processor on these two boards is LPC932.
I need second processor because of complexity of design and isolation between two processors. The third design is LPC932 only. I'm using that thing for I2C slave communication with the board.
I'm using LPC because of low cost. F001 costs ~$5.3/10000pcs, LPC932 costs $1.8/1000pcs.
I don't like Philips/Atmel entering into ISP thru serial port. I finished couple designs last year on that way and it worked for me.
I like more JTAG approach. But, I like PHILIPS price.
Thank you,
Goran