The 5+ is for the stunning city - I'd rate the service and attitude of it's inhabitants at 2 at best. Be prepared for a very frustrating session with the passport control, impressive modern terminal staffed by a stroppy unpleasant team that opened and closed channels when they chose and delayed disembarkation by as much as they could.
Once on your tour (the only way to go without a visa) the guides appeared to be keener to get you to the souvenir emporium of their choice than showing you the truly breathtaking city.
Highlights, The Church of the Spilled Blood, the interior of St Isaac's Cathedral, the view across the Neva River to the golden spire of St Peter and Paul and of course the Hermitage and the Winter Palace.
Lowlights - Street vendors - very pushy, don't try going off on your own in the Hermitage even if the guide says that's fine, a rather vicious babushka will have very different ideas. Also don't try asking for a second bottle of water with your lunch, you may well offer to pay but it is not authorised under any circumstances!!
Do visit the fantastic Singer Sewing machine building (now a bookshop) on the Nevsky Prospekt near the Church of the Spilled Blood. A Beautiful Art Nouveau building. Do go to a Folklaw evening - the costumes, singing and dancing is superb.
If we went again we'd do an independent tour out to Catherine's palace and Peterhof as the reports from fellow cruisers said this was great.