TA here.
Worst things....
The constant watching and observations. Walks looking at our boards and classrooms. I am a neat freak, so is my teacher, but there is less and less time to do the job in the hours given, so I often do unpaid overtime to get little jobs/boards done.
Zero tolerance for violence being introduced - but often no SLT around to deal with the perpetrators.
Less funding = less staff. Not good for inclusion at all. SEN children left to manage when their 1-2-1 TA is used elsewhere.
Class TAs doing a thousand and one things, expected to look after the needs of many (often conflicting needs), and complete all classroom tasks as well.
Staff leaving = not replaced. See point above.
Coasting staff. Add lazy too. Boils my piss when some staff get an easy ride. 
The children who constantly talk while you are talking, or you have asked for silent work. Repeatedly = Low level disruption that grates on a daily basis.
Best things....
Engaged in a brilliant lesson, with the kids enthusiasm giving you a buzz.
Using my creativity, as I construct a trolls bridge from cardboard.
Learning a musical instrument with the class - and the children jumping up to help non-musical Miss. 
Feeling emotional and full of pride, as you watch your beloved class perform a play/song.
Seeing their faces after a half term, and realising how much you have missed them.
❤❤