I've lived in many places. Grew up in Northern California. Lived in japan and Asia for several years. Lived in DC and Maryland. South Dakota and Texas. And Tucson, twice. This time it's for good (unless climate change forces and exodus).
Is it hot? Yes. There are two months (June and July) where the heat is seemingly unbearable. One just needs to be wise about how they schedule a day: up early, inside mid day, back outside at sunset.
Aside from those two months, the weather is beautiful, as is this desert. The Sonoran Desert is rich with life, both in plants and animals. It really is a nature lover's dream. It's not fair to compare it to a lush forest or an ocean shore. It's neither and never will be. But it has its own unique and diverse beauty. The mountains to the south and north provide a break from the desert. In fact, the view from many part of Tucson of those mountains is absolutely breathtaking. People who like to hike won't be disappointed in the year-round opportunities.
Culture and things to do: what is the saying about boredom? "Boredom: the desire for desires." There is PLENTY to do here in Tucson, if one just broadens their interests a bit. There's the standard movie theater, malls, etc., of course. But beyond that, Tucson has a rich music scene, from indy bands to a Symphony. Pick up a copy of the free Tucson Weekly or Downtown Tucsonan and see that there is ALWAYS something going on in town.
The downsides to this town: sprawl and climate. As mentioned before, climate change could be the death of this place, especially as oil becomes scarce. But for now, it's a town with heart surrounded by a diversity in nature worth fighting for.