Hi Rob,
I live in Vienna, and took the boat ride to Bratislava with my wife two summers ago. Forget worries about security, ukraine etc. Bratislava is 50km from Vienna, the safest million person city on earth. If is 1 1/2 countries away from Kiev, which is a half a huge country away from the conflicted parts of Ukraine.
It is a nice city. the day of walking around was great. You will end up walking up to the castle which was burnt down about a century ago, and newly rebuilt. Didn't have much in it whe we were there.
Walked around the town, looking at buildings. Had a long lunch in the pedestrian zone. In the after took a long walk along the bank of the Danube, which has modern promenade with lots of shops, cafes bars etc. On the day we went it was really nice and sunny (at least till the late afternoon thunderstorm) so we didn't bother doing museams and indoor sites.
If you want to be more flexible, and save some dough, you can also take a train, rather than the river boat. The trains go much more often.
Mark
