Greatest part were the conversations and the people - there are good people who work for this company.
Hardest part about the job was feeling underappreciated or undercompensated and your manager not realizing the value you are actually providing let alone the skills set, knowledge, and dedication which you bring. If you are in a position where you are constantly training someone who is supposed to be better qualified than you, who has a bigger title than you, who gets paid more than you, and who works under the same group/department and your boss doesn't realize it, then your boss should get fired. If you roll up your sleeves to do the work required even if it's outside of your expected assigned duties to help meet crucial deadlines and everyone but you gets a bonus that period, then you have a boss who is either greedy or has truly undervalued your worth. Either way, it is insulting and damaging to employee morale.
Your responsibilities could expand tremendously but if there is a salary freeze (and there had been many as the company worked through the recession and then some), don't expect any sort of raise.