Mary and I have just spent 10 days in St Petersburg and Moscow. We were a little apprehensive about what it might be like but it really exceeded all our expectations.
One word of advice: don't try Russia without some structure and back up. We chose Trafalgar Holidays and really enjoyed every moment. We saw most of the tourist highlights including the Winter Palace, the Kremlin, Red Square, Putin's Palace, Peterhof and St Catherine's. All were stunning and awe inspiring.
One of the unexpected highlights was a tour of the Moscow underground. One minute on an escalator going down at nearly ninety degrees is a mindblowing experience!
Give Russia a go, I would recommend it.