I rode through Czech Repulic and Poland in Summer 2013.
The main motorways were fantastic ( probably due to them hosting Euro 2012 the year before ), but the trunk and minor roads were often shocking ( lumpy/missing tarmac the biggest issue ) and would just stop for roadworks with little or no warning. There scenery was much nicer and it was a much more interesting ride, stopping off in little villages for a coffee and a break.
I didn't have an issue with theft, as I took the panniers and topbox off at night and the bike was chained to something solid with an Almax and Squire combo. Wasn't going anywhere in a hurry @tu*
The worst problem I had ( and this seems to be the case the further east you go ) was with general shocking driving standards and more than a few drivers who were clearly pissed at the wheel. I was on a fully laden Tiger Explorer, well above the posted limit on an overtake and an impatient Polish rider squeezed between me and the armco at some silly speed, missing me by inches !!
Auschwitz and Birkenhau were well worth a visit. It's an emotional rollercoaster, but something I think we should all witness.
There is a salt mine nearby that's worth a visit too. Very interesting. @tu*