I visited this WHS as a day trip from St Petersburg in September 2017. The old city of Veliky Novgorod lies some 200km away from St Petersburg and is quite easily reachable by train, bus or car.
Since I wanted to visit early before the very few Russian tourists and since I found a good chauffeur service offer, I opted for the latter and arrived at around 9am. The Kremlin opens at 6am but all the buildings are accessible as of 10am, apart from the main church where a lovely Sunday mass was being celebrated. There's just a small billboard stating Novgorod's inscription on the WH list but no plaque.
After a short stroll around the buildings within the Kremlin, I headed towards the bridge which crosses the Volkhov River and which leads to Yaroslav's court and marketplace. The panoramic view from the bridge is breathtaking on a sunny day with the red Kremlin wall and the church onion-domes (photo). There are a number of pretty old churches with different Russian architectural styles opposite the Kremlin and some have very old frescoes still visible. The cathedral of St Nicholas is worthy of mention for its colourful fragments of frescoes from the 12th century.
If you're not in a hurry I recommend walking around the Kremlin walls to be able to appreciate the different towers. In the afternoon, I also visited the Yuryev (St George) monastery and the colourful interior of the Cathedral of St George.
All in all I really enjoyed my visit here and I would rank it on the same level as Sergiev Posad as a WHS.