I actually have STM32Discovery with Cortex-M3, and there are numerous problems with connecting this to IAR or Keil (as a matter of fact I didn't try Atollic IDE). I generally also thought that STLink is only for SWD interface, not classic JTAG, maybe I'll have to double-check that.
What I actually want is universal JTAG to use with ARMs from ST, NXP, Texas, EnergyMicro and others as well as Altera, Xilinx and Lattice programmable logic devices. currently I'm kind of eager to try Cortex-M0's from NXP (LPC1111 in QFN package costs about the same as low-range ATMega - LOL@that). For hacking with FPGAs, CPLDs and so on I'll probably have to use some twisted OOCD/GDB/CDT/Eclipse voodoo, but it would be nice if i could develop with ARM MCUs using Atollic, which is much more convenient to use.