Noise levels and cooling
Hopefully Dell has learnt a lesson from their 11G tower servers which caused a lot of customer complaint re. noise levels (something that is probably of little concern for a rack server, but rather important for a tower server). The 11G servers suffered from fans blowing out cold air as the thresholds were set too high. Some Lifecycle Controller firmware updates somewhat improved the situation a bit but the servers are still awfully loud.
And it would be great if they also imrpoved airflow over the expansion card section, which was just painfully poor in the PE T410, T610 and T710.