I heard many complaints about Jane Foster as a hero. While I get it that her being Thor was a bit bad for original (I still think it was well written but that's not the point), I really like her as a Valkyrie.
First of all, Valkyrie tranformation was a pivotal point of her character arc. As we remember, her Thor transformations made her unable to cure cancer. Ultimately, she sacraficed Mjolnir to save the day, resulting in her death of this disease. But after death, her courage was rewarded when she became a Valkyrie. I think that it was a win-win situation - Thor became Thor again while she received a glorifying conclusion of her character development.
Another concern that was raised is that she stole the mantle from Brunnhilde. However, she explained it pretty well in Valkyrie: Jane Foster #5. She said that Valkyrie is not a name but a job.
What's more, the one who she reportedly stole name from said the same thing. There were many Valkyrior on Earth-616 alone, including Dani Moonstar, so I don't have a problem with her being another one. Plus, anyone who misses Brunnhilde had a chance to see her being a guide to Jane from the first issue.
Another thing I like about her are her powerset and equipment. I'm not talking only about free flying horse (Jane received when she was forced to break Dragonfang).
While Brunnhilde was cool with her Dragonfang and all, Undrjarn, the All-Weapon is even better. It's part of Jane's body and can take form of any weapon or wings. It was really useful in issue 9 of her adventures when she used it to stop corruption from Øde's tomb.
But the most interesting power this Valkyrie has is something she calls 'Death Stare'. It allows her to see the death of people. I don't know if Brunnhilde had the same thing but I surely like it.
Last but not least, story in Valkyrie: Jane Foster is more unique than in Jane Foster's Mighty Thor run. While as Thor she does anything Thor's duties are, as Valkyrie has more interesting ones involved around death. For example, she travels with Heimdall through the afterlives so he can rest in peace. Another time, she cures Death Herself with other Marvel medics. At the same time, Jane works at the mourge, which fits her as a warrior of the dead people.
So, these are my reasons why I think she's better than you might think. And if you still don't like it, there are still synergy Valkyrie and King in Black: Return of the Valkyries for you.