[johncal]

I can tell you this much.

I have upgraded to MR1 and did a full restore with SPB Backup and everything went perfectly. Everything restored and worked exactly as before the ROM upgrade. The only thing you have to reset is your power options. For some reason it goes back to stock settings for that. No big deal though just a couple of seconds to reset. The reason this goes so smoothly however is most likely due to the fact that the MR1 update is mostly fixes for the stock ROM and mostly everything from the original ROM version is left in tact.

My findings with MR1 is it runs slightly faster and smoother, however it also starts out at about 8-10% more memory usage than the previous version however doesn't seem to leak as much . Battery seems fine.

If I have any long term adverse effects, I'll post them.

I would say there are no guarantees if you do a different version ROM upgrade, but you could always do a restore and if it doesn't work, do a hard reset and then load everything by hand. At least you've got a shot... if you have the courage to try it.