I travelled for ~3 weeks in Myanmar in November 2009: Yangon, Mrauk U, Mandalay region, Inle lake area, Bago and Bagan.
If I'd return to Myanmar, I'd spend much more time in Mrauk U. It's out of space and out of time.
I wouldn't return to Bago, though it was still interesting in its own right.
A town I can recommend is Sagaing, near Mandalay. It basically is a series of hills stuffed with small monasteries (mostly modern though). I took a motorcycle-taxi to the top and hiked downwards to the river, stoping here and there to have a chat and thee.
Inle lake is very beautiful. One day I hired a boat to visit places around the lake. The next day I hired a boat just to wander around to photograph the fishermen. It's important to get out as early as possible.
Bagan is impressive. Get out early and stay out late. If it is for photography you go there, scouting the area is extremely important. Most people visit the large temples at sunrise and sunset, but there are so many small sites with an accessible top roof that will be yours and only yours... You can buy maps of Bagain with all the sites indicated (from the big pagodas to the smallest shrine). I suggest you buy such a map and indicate where you want to return later when scouting. I was in Bagan for 5 days. It was not enough... I think 3-4 weeks would be nice, seeing the sun set and rise from different locations. Also, Bagan is magical at night. There is only very little light polution in Myanmar...
I am currently making a website and have finished my travel photography galleries. You can find the Myanmar gallery here:
myanmar.fotomachi.comGood luck, Myanmar is a delightful country to photograph.