I have travelled to Shimla from Delhi ISB Kashimiri Gate Bus Stop, boarded the bus at 9 Am in the morning reached Shimla at 5 Pm. The journey was an amazing one the bus we travelled is a Volvo bus it is an multi-axle sleeper 2+1. The condition of bus is good, there were many dhabas in the way, the bus took a halt after reaching Karnal had our lunch at one of the dhabas. The bus had charging points, pillows and water. We reached Shimla by 5 Pm the next day visited Kufri. Visiting Kufri is best if it's having snowfall, otherwise one will find nothing there.
But if you are going to travel Shimla for very first time, then you can consider visiting it, but I'll suggest you to visit other areas near to Shimla too.