Good all round
Whilst it's a nicer way of getting from Southampton up to Bristol than the A34 / M4, this is just a pretty average A road. If you are travelling that way, you're nest avoiding the boring bit near Bath, and heading across the mendips towards Cheddar.
Too busy most of the time, along with fighting your way through Salisbury and Bath means no longer a good run. Also cameras and police on route.
A much nicer way of getting from the end of the south up to bristol, rather than going all the way up the a34/M4, with not much of a time difference. Lots of gorgeous scenery, some wicked bits of road, and some really hard to spot cameras near Salisbury(They're CCTV ones not big yellow Gatzos) managed an average of 50mph in both directions, even tho it was busier on the way back.