So, I wrote the code for the first question (life/universe) in Java in under a minute. It took me over half an hour to get it working during the submission process.
It would be nice if the system provided a decent bit of feedback, e.g.
My first fail was because I didn’t call the class Main (I know now it’s in the FAQ but they could easily parse the file to check for useful common errors)
My second fail was simply ‘runtime error’, which turned out after much scratching to be simply I’d left in my package details at the top of the file.
I think most faults would be easier to find if instead of ‘runtime error’ or ‘wrong answer’ with no means of knowing, the submission system provided (in the case of Java/c#/c++ at least) a stacktrace of any exceptions found.
The other problem is it’s quite hard to write nice code due to the limitations of having to submit bare code (i.e. I wrote a harness to determine times, debug info, etc to wrap around the code but for codechef I have to get rid of it all and put everything in one file). I use this for project euler so I didn’t really lose much code.