We thought about it but eventually went with the tours arranged on board. I think we made the right decision, they were well organised and the guides were of a high standard, all local people with a vast knowledge of their given itinerary. The only reason to go independant is perhaps to save a little money, for what its worth stick with celebrity tours you wont be disappointed. Don't miss Peterhof and if you are an art lover the Hermitage is very good.
We arranged a private St P tour along with an American couple in summer 2007 and it was worth every rouble ! They picked us up from and returned us to the docks each day and we saw all the sights we wanted to see in the comfort of a small Mercedes vehicle. The guide (Tatyana Churikova) was terrific. She spoke excellent English, was extremely knowledgeable and managed to avoid queuing at all the attractions. Overall, it was quite a lot cheaper than the cruise line (RCCL) tour and provided a much more personal service. The only downside was the need to obtain personal Russian Visas (not required for a cruise line tour) - we were a little pushed for time and so had to visit the Russian Embassy in London and pay the higher price for an expedited service.
Further details at: http://www.tour-stpetersburg.com/.
We booked a two day tour will Alla Tour (www.alla-tour.com) last September and they were excellent. They have a very good website through which you can make bookings and they will answer any questions you might have via email. We were met at the dockside on both days. Day 1 - brief tour of the city, St Peter & Paul Cathedral, the Tsars Village and Catherine's Palace (which is some way out of St P), Peterhof and the Fountain Park, return to city via hydrofoil and then shopping. Day 2 - early entry to the Hermitage missing the crowds, Church on the Blood, St Isaac's Catherdral and Yusupov's Palace. A packed lunch (not memorable) was provided on day 1 and we had lunch in a Greek!! restaurant on day 2 which was OK. Our guide was excellent (she was a professor of English) - her knowledge of St P was immense. There was no need to apply for an individual visa - Alla arranges a group visa and this is included in the price of the tour as are camera permits for the sites visited. You only need show your tickets to the Russian immigration authorities to prove that you are covered by the group visa. Alla will also arrange evening visits to the ballet/folk evening. Other independent tour operators in St P are Denrus and Red October. Hope you find something suitable. St Petersburg is wonderful.