I actually dropped Thor when he took over. I don't like his art nor his stories. What's the appeal?
I know people liked seeing ancient mythic elements like the goat-chariot. I didn't. Goats are silly. I think people liked his costume designs, which I did too. I think his stories were more magical and less scientific, right? Was this a draw?
I'm with you, AC. I don't dislike Simonson's Thor, like I do his Fantastic Four, but it's not my favorite. I bought Thor sporadically in the 80's and picked up most of the run later on. I guess it starts with his artwork. I enjoy DeFalco/Frenz's run more because it's a blatant throwback and because I like Frenz's art style much better. I think it took Lee/Kirby awhile to get going on the title but once they did they produced great stuff. Len Wein and Roy Thomas did good work, too, but you could say that about almost every Marvel title in the 70's.
As for Simonson, he wrote some good long term stories, but I never found Beta Ray Bill that appealing and Simonson's humor often left me flat. I feel his Thor run is good but overrated.