Though I had read enough to know that they were completely different places, I framed a lot of my expectations for St. Petersburg on a previous trip to Moscow. My experiences came to be defined first and foremost by the great company I enjoyed, and to a much lesser extent to the total absence of darkness (reference to continual daylight not the occult).
There is no shortage of things to do in St. Petersburg. It is a city that truly shines with its royal heritage. The architecture screams of old world Europe and the myriad churches are regal in the marriage of the east and west. The Hermitage rivals any major museum in the world. The vodka flows freely. And, if you go in July it never gets dark. I personally never realized how reliant my rhythm was to the visual cues provided by the sun. It's certainly easy to stay out late, when you have a limited concept of how late it is.
The people are St. Petersburg appear stoic as you walk down the street, but are genuinely warm in their interactions, with the possible exception of some of the cabbies. The service is slow, but not bad. The local food is better than the foreign restaurants.
It's always a little challenging for me to go to a place where I lack both any understanding of the language and any familiarity with the alphabet. That being said, I think it is a great challenge to relish on an international adventure.
On the whole, St. Petersburg is definitely worth seeing. I had an amazing time. It doesn't qualify as one of those places that touched my heart and I could always return, but I would certainly encourage others to experience this destination, in the summer, despite the night's absence.