I went 2 years ago for 3 weeks and loved it.
It's optional to have a tour guide, but definitely would recommend it as they can tell you a lot about the history and culture. Alternatively, some good drivers can double up as a tour guide.
It's definitely a place to go now before it really opens up to tourism (currently, they have less than 1 million tourists annually).
It's not a cheap country by any means.
We did Mandalay, Bagan, Inle Lake, Ngapali (a beautiful beach resort), pyin o lwin (North of Mandalay), Hsipaw, golden rock, and Yangon.
Yangon was my least favourite. All the others were unique in their own right and would highly recommend, including the hot air balloon over bagan temples.
What I loved the most was the people. When you read about it online they do advise tourists not to ask local political questions but over the last few years it has actually opened up a bit more, so people are happy to talk about it and give their views.
We were afraid we would be templed out, from all the temples, but it was actually fine.
They still use a lot of the infrastructure the British developed 100 years ago, which is also quite interesting.
Happy to answer any other questions you have.