Is it bad form to use the word exciting in a paper, when discussing other people's results?
An established rule on proper writing demands to "show, don't tell". This does not mean that your results can be left to "speak for themselves", but it suggests that rather than simply claiming that your results are exciting, you should demonstrate and argue why they are. The onus is on your interpretation.

Moreover, the attribute "exciting", just as "interesting", is particularly trite because it is over-used and terribly vague. It begs the question as to what it is that is so exciting.