and is arduino hardware or software?
its both a nice breakout board, and a software package to make it easier to start in the world of micro's
keil, which I have not seen until just now, seems to be akin to AVRStudio for the avr's like what the arduino uses, though its much less freindly to a new person, but also keep in mind that comparing an Arm to a atmega is like comparing a Pentium 4 to an Apple II