It will be our second visit, having spent a couple of nights there in September 2010.
One major objective is three nights at the opera.
It's a charming city, though, and we agree with the comments here:
As you arrive at the Main Train Station, you'll see vineyards on the slopes of the Little Carpathian Mountains, where they meet the Danube River. The Austrian border is almost within sight of the city and Hungary is just 16 km away. Many beautiful monuments survive in the old town to tell of its past under Austro-Hungarian rule, and Bratislava's numerous museums are surprisingly rich. Franz Liszt visited Bratislava 15 times, and the opera productions of the Slovak National Theatre rival anything in Europe. Bratislava is not as swamped by tourism as Budapest and Prague.