Let me start by saying that the Temple of Hathor at Dendara is lacking in hawkers, aggressive guards, and has a peaceful garden. For tourists in Egypt, this means that a trip here will feel like you're going to a resort. You won't be beset by anyone trying to get you to buy souvenirs. The walk through the 'gauntlet' of souvenir vendors can be easily bypassed. In terms of experience, this is already going to be the best in Egypt.
However, inside the Temple is incredible. Well preserved and filled with wonders from those times. There's a minimum amount of vandalism, unlike other places such as the Luxor/Karnak temples, and not only is there a roof still, you can actually walk up the steps and come out on the 'second floor'.
Getting here without a group is hard, so you'll likely have to take a tour. But for the quality of both the history and the experience, it's a must see.