Congratulations on getting accepted! I'll put in another plug for Hack Library School (the Hack Your Program series is especially useful if you want to get a better sense of current students' impressions of their programs). You might also try getting in touch with students or alumni from your program to see what they say about their experiences.
On to your questions...
I really enjoyed doing my MLS. I learned a lot, and was able to undertake a specialization program that matched my interests.
Not sure I have a straightforward answer to this one. I think the difficulty varied a good bit from semester to semester. I also took some courses offered during the shorter terms (winter, summer), and those were all fairly demanding.
I worked pretty closely with an advisor, but that was probably due to shared research interests and the structure of my specialization program. From what I could tell, the level of communication with an advisor depended a lot on students' preferences and individual programs.
Nope.
A lot of my classmates worked full-time, but I noticed as I went through that the number of people enrolling straight out of undergrad increased. Many of my classmates were current library paraprofessionals, some were making career changes (teaching and journalism seemed to be among the most popular first careers), and still others were working in another field entirely. They represented lots of different life experiences, perspectives, etc.
My core classes stressed group work. People mostly pulled their weight. There were occasional miscommunications, but nothing that wasn't easily resolved. Also, we did a lot of our group work remotely and coordinated via email, which (at least for me) made it more manageable.
Yes! So many! They're really completely different beasts.