IAR user here.

I cannot complain about the ease of setup and the code generated by their compiler, and the newest incarnation of their linker uses a less cryptic format than the older version I know.

However, beginning with version 5.50, I started having display corruption+crash to desktop issues with the IAR IDE, and have not been able to resolve this problem despite a lively email exchange with their support, sending post-mortem dumps from a debug version of the IDE, and telling them quite exactly that the problem must have crept in between versions 5.41 and 5.50 of their IDE.

The issue might be related to my computer still running under Windows XP, since a colleague of mine (also running Windows XP) experiences the same problem, while others (running Windows 7) do not.

It's also fairly easy to tell whether the version in question will show these problems - after starting up, the separator bars in the toolbar aren't shaded correctly (too much white) in versions that will crash. I assume they have some sort of pointer or memory issue in their handling of on-screen graphical elements.

Unrelated rant:
Have any of you ever seen the line

#define then
 

in a piece of "serious" C code?