The road alongside lake thun is a fun ride with a good view on the lake and the surrounding mountains. The surface is worn out in parts, but you won be able to drive too fast either way. There is a lot of tourist traffic, so you won be able to get your knee down on weekends.
Despite all the bad things you should drive along lake thun and lake brienz if you are in that region, the view alone is worth it.
Beautiful road at sunset, the road runs right round the side of Lake Thun and avoids the Mway on the south side (also means no need for a Swiss highway robbery vignette). Watch your speed, the Swiss Plods are not known for their understanding nature.