3 days is fully enough for Yangoon.
we took over-night train (we love rail-travel generally in Asia and much better then buses) to Mandalay. You do have THE attention there as station manager personally sell you the ticket, take you through security barriers to the wagon doors and say goodbye. It was most expensive ($50)and most luxury wagon (within Myanmar public transport) but still a bit rough (if you know Thai or Malaysian 2nd class trains - those ARE better than Yangoon-Mandalay super-grand coupe express train). Large double-bed in the coupe though (plus entry hall, shower cubicle and toilet cubicle - all quite dirty or normal, depending how you measure it). Very slow 15 hour journey (kids jump on and poke into the windows
). a bit exotic for 1 time but I would better fly next time. Stock up on food and drinks - it does not stop anywhere (officially) so we starved a bit!
Mandalay is a huge city but I would say 1-1.5 day is enough for it. but dont rush. All main, nice and interesting monuments and temple complexes are spread outside the city (all within 10-15 km from its centre) so 3-4 days would be good to see those without rush. I was not so impressed with Mingun (shown on Lonely Planet guide front page) as by monastir complexes on the hills down the river.
Took a touristy boat (prices are much higher vs local boats so not many locals take it, they could be put off by toilet signs "Foreiner only"
) to Bagan. Whole day trip, wide river and you see bits of life in the villages and fileds around. ok-ish (I heard same 12 hour trip by bus is a torture as roads are bad there).
Bagan is something really really special. I cannot describe it's magnity and shire size. Sunrise or sunset (we woke up and stayed on for all of them!) are absolute majic there. We were there 4 days (incl New Year celebration with local kids singing for us by the open fire!:-: ) and saw pretty everything but I would take even slower pace next time. We used horsecart and this is definately thing to do (try to find horsecart #318, guy with name Wyne - good english and very helpful), or bicycle. We spent the whole week in Angkor this year (just returned) so I would stay for 5-6 days in Bagan next time and just enjoy it slowly. We'll take that baloon ride next time for sure. It is a life-lime experience and you will never forget that sunrise flight over hundreds of temples poking through the fog as sun comes up with orange light.
Took a flight to Inlay lake (planes are actually ok if you take Air Bagan or Air Mandalay) and stayed there for 4 days. Found great local guide Tanzin (he and his wife runs a small pharmacy aka travel office in the main street - please please say him hello from Mish&Kira - we were there in Jan 2006). He took us around on his long-tail boat (he was brilliant to avoid tourist hords and get to best places while nobody was there) to local villages nad local markets, went up to the hills for whole day trek, paddled us around through small channels, took us for lunch to local families and just helped to show how people live. It was a biut chilly in the mornings but ok during the day (Inlay is quite high and remote).
Flew back to Yangoon and then stayed a week on a Thai beach to relax after greatest Asian holidays so far.
I think Myanmar is a gem. People have different views about their government and "regime" but I saw much more police on my return day back to London then in the streets of Myanmar during 15 days. It is safe there, people do respect and like tourists and it was definitely much much safer then in many streets/areas of London or NY. About that political lady - I am not sure that some democratically elected (or skillfully promoted) presidents do the best for their people, countries or world. I have example of Chile (1970s), much of Africa, some Eastern European countries or some other very recent examples of countries where communists or democrats or freedom leaders have had no clue how to manage their country, how to run economy and what to do after election celebration, followed by things turning into nasty civil wars, lootings, killings etc etc. Let is be where we are now and we'll see the future. I want to go back to Myanmar soon rather then hear stories about civil wars, powerless democratically elected leaders or other countries bringing western democracy operations. I wish you visit Myanmar and see it as it is now.