I'm a 2nd year analyst at Deloitte. My answers to your questions as follows...
(1) The majority, yes. As at any organisation, there are a few bad one's who you have to keep a close eye on when working with them.
(2) I've found them very helpful so far - some Partner's can be assertive/aggressive, and may not have the same level of tolerance or acceptance for mistakes made through youth/lack of experience
(3) I've found the work life balance great. When the work is on and deadlines are approaching, you will work hard. When it's "business as usual" - you are okay to do as you please. At these times, I quite often work from home - although this is not encouraged, it is carried out by many practitioners.
(4) Very good. Good flexibility in terms of working in different service lines etc, funding for Professional exams such as CIMA, CIPS, IDM etc.
All in all, very good company to work for.