I've visited Tallinn and Riga, and I hate to say it - but Vilnius isn't as pretty. It has plenty of interesting buildings, but it doesn't have the history I guess.
The main city square has the Cathedral next to it, which is deliciously cool on a warm day. Interestingly the Cathedral has a bell tower, but it's not connected to the main building. It stands alone and proud on the square. I'd guess that there are some good views to be had from the top, but it seems to be locked up.
Vilnius does have a curious secret, and that is within it's environs lies an independent nation - Užupis, which has unilaterally declared independence and has it's own constitution. Although I collect countries, I don't think I can count it!
I did get a telling off by a local while in Vilnius. I popped into a church while there was a service taking place, not wishing to disturb anyone I sat down at the back and waited for the service to finished. While I did this an entire tour group came in, wandered around the church took photos and then left. At the end of the service a baboushka came up and slapped me on the shoulder as I was sitting with my legs crossed! Oh well!