Hermanus is a lovely spot, but its essentially a small town. Spent 5 nights there in 2008 and I think there is only one late night bar. If even. We were there in the middle of the Whale Watching Festival ( a busy enough time for the town and it was still quiet!) Would definitely recommend it but don't go there for night life!
Once you hit the coast on the drive from Capetown to Hermanus, the scenery is fantastic.
We stayed in Capetown for 5 nights also and I would recommend it as a base for getting around. Plently of shopping, nightlife and lots of lovely restaurants also. Some fantasic beaches just south of Capetown too.