...and can tell us how it's like? Are the roads okay, and how's the traffic? We've heard prices for hotels are very high (35_40$), and sometimes very far from the next one.
Idea is to cycle from Tachileik via NH4 to Inlet lake, then north to Mandalay, and via Pagan down to Yangon, then back to Bangkok. I'll guess that's the usual route?
In the moment we're in Sichuan and hoping for warmer weather:-) :-)

There was discussion on Bruma some time back, it might give some info, the OP provides details of his trip.
http://www.lonelyplanet.com/thorntree/thread.jspa?threadID=2317054
you might want to check recent border openings. i've read there are now 3-4
crossing from thailand, and it may be possible to continue on to the interior.
not sure about mae sai/taichelik. i think there you're still limited to only as
far as kentung, then need to take a flight.
.
perhaps check into the crossing at ruili, yunnan province. if you can cross
there, it's a nice ride to mandalay. and you can pick up your visa in
kunming as there currently is no VOA.
.
things are changing, but there are still many restricted areas. very limited
roads you can use. even if you can take the road, there may not be any
guesthouses available. foreigners still must stay at the relatively few
authorized places. the road south from bagan to yangon is open, but
there ain't no guesthouses. you'll need to take the eastern route via
thazi, and there's still a long stretch south of there with no lodging.
.
otherwise, roads are in good condition, traffic mostly light.

I am cycling right now. I flew into Yangon and been riding up. Now in Magwe. I have had no problem staying in small towns along the way, including mostly non-tourist towns. Sometimes they have to call up the local immigration or police department and get permission, but no problems so far. In Taungdwingyi I was told at one hotel that they were "full", which I didnt quite believe. But the other hotel accepted me after calling up immigration and getting permission.
Not much traffic on the roads. These are sometimes narrow and in poor condition. Lots of shade trees. Not much traffic, but drivers are fairly aggressive and occasionally chase you onto the dirt by the side of the road when they are passing. They also honk a lot.
I have paid between $10 - $25 for hotels so far, with $20 (or more precisely 20,000 kyat) being the average. But for this you get a pretty good room with AC and often TV with movies. I think that Mandalay (and maybe Inle) are more expensive. Food is very inexpensive -- perhaps $1 - $1.50 for a big meal.
I never see any other foreigners (but I will soon be in Bagan). Nobody speaks much English. People very nice and try very hard to please you, though.
Occasionally, there are police/immigration checkpoints along the road. They ask to see your passport, but no threat to prohibit you from continuing. Occasionally, small town police follow behind or ahead of you for a while on their motorbikes. Not sure if they think they are keeping an eye on you or are giving you an honor guard escort. They are friendly, too, although the first time it happened it was slightly unnerving.
As for your planned route, I am not sure what the situation is. Tachilek to Taunggyi has traditionally been a restricted road. Things are changing very fast here, so it is possible that the road is now open. I very much doubt that you will get any good information on this. The road down from the Chinese border at Ruili/Muse should be no problem (but I have not been there yet).
Hope this was helpful.
