I booked a day trip before with Rabbie's and had a great experience. Again I wasn't disappointed. Rabbie's booked the train ticket with reserved seat from London. Our driver Dom picked us up in Penrith in a small comfortable bus. He was very organised and knowledgeable. He didn't hesitate to add some stops for great views when we had the time and shift things around to dodge the rain for the photo ops. That is one thing to note. It can sometimes rain a lot there. So bring waterproof gear. That being said, this is still one of, if not the most beautiful region in England. Well worth dealing with the less than ideal weather.
As far as accommodations, we stayed in fantastic B&Bs in Keswick. While the tour also tends to stay in Windermere, it was peak tourist season so it would have been crowded. I was thankful that Keswick was cute and small with a decent amount of options for dinner (reservations are recommended though for many places).
Overall, we hit all the most important places to see and there was enough diversity of things to see (not just water). The optional activities are not too expensive and I think worth it, especially the steamboat cruise and the visit of Beatrix Potter's house.
I think this tour is great if you are visiting the UK and want to see something other than big cities. It's also great if you live in the south of England but have never been to the Lake District, especially if you don't have a car and/or don't want to drive yourself in the mountains.