I have just had a chance to try the beta of RobotC (download it from their website: http://www.robotc.net/). You will get a 120 day trial (Nice!) It is still in Beta, but it looks really good.
So far, it downloads a chunk of code to the Arduino (I am usimg a Uno) that lets you debug (single step, etc) right on the Arduino!
There is supposed to be a simulator too, but I haven't tried it yet.
I would definitely call it "featue rich". The editor looks very nice too.