I visited this WHS in November 2016. It is a great mix of Dravidian and Rekha-nagara styles but in terms of size it is more comparible to Khajuraho than Hampi.
I really enjoyed the main temple complex of Pattadakal consisting of Galganatha, Sangamesvara, Virupaksha and Kashi Vishweshvara temples as well as several remains and minor shrines. Near the main complex lies the beautifully sculpted Papanatha Temple with a raised podium and superb Ramayana sculptures on the Southern wall (best to visit in the afternoon for photography).
About 3km away is the Jaina Narayan Temple which has recently been completely dismantled, numbered and painstakingly rebuilt stone by stone. Due to recent floods, the walls have become darker and the humid and dark interior has attracted several bats.
All in all Pattadakal is a very interesting WHS but an extension with Aihole and Badami will really boost this site's OUV in my opinion.