Her +1 is similar to that of Nissa, Worldwaker’s, in that she turns a land into an Elemental creature. However, there are some important differences with Vital Force’s +1. First of all, Worldwaker’s ability makes that land permanently a creature. This +1 only makes that land a creature until your next turn. However, you get a 5/5 with haste instead of a 4/4 with trample. She also un-taps the land, which essentially could give you an extra mana if you decided instead to tap that land for mana instead of attacking. Functionally, this is a similar ability, although the permanency and trample that Worldwaker’s +1 offered is better in some cases.
Then again, when Nissa, Vital Force first entered Standard, the man lands Hissing Quagmire, Lumbering Falls, Needle Spires, Shambling Vent, and Wandering Fumarole were still in Standard. Her +1 ability actually worked well with these manlands, as not only would they become 5/5 lands with haste, but gain any abilities that they would have if they were activated. For example, Lumbering Falls would still gain hexproof, meaning opponent’s couldn’t target it with spells. Hissing Quagmire would still have deathtouch, Needle Spires would still have double strike and Shambling Vent would have lifelink. Wandering Fumarole’s ability to switch power and toughness wouldn’t really matter, though. Those man lands wouldn’t stay in Standard long with Nissa, Vital Force, but when they were, she had fun with them.
Vital Force’s -3 lets you get a permanent card back from your graveyard to your hand. This isn’t a bad ability, but going from 5 to 2 loyalty right away seems like a fairly high price to pay. However, this ability can be useful in certain situations. But paying 5 mana for this Regrowth ability right away doesn’t feel awesome. Still, it’s a mode that will probably be used at certain junctures of the game, so it’s a decent second ability. It’s nowhere as good as untapping up to 4 Forests, however, as Worldwaker could do.
The ultimate ability is the one that has most players excited. Essentially, it’s a Horn of Greed that only benefits you. Drawing a card just by having a land enter the battlefield under your control is really solid. Note that you don’t actually have to play it, meaning that cards like Splendid Reclamation that bring lands into play does the trick, too.
Horn of Greed, an artifact most recently featured in Conspiracy: Take the Crown, actually only draws a player a card when he/she actually plays a land. It also helps all players and not just yourself. For only -6, this is a really good ultimate. With how easy it is in Standard to put land cards into your graveyard to use Splendid Reclamation, Nissa, Vital Force looked like the piece that deck needs to be really good. (That never really happened, but it could have.)
Nissa, Vital Force is a really solid planeswalker. The ultimate ability is actually quite good, as is the +1 ability. I’m not sure how I feel about the minus ability, although being able to retrieve any permanent card is handy. With 5 loyalty and a CMC (Converted Mana Cost) of 5, it seemed a sure thing this Nissa would see play, perhaps even in Modern.
But, what really happened?
Indeed, Nissa, Vital Force has seen play, notably as a one-of in some Saheeli Rai / Felidar Guardian Copy Cat Combo decks. But most consistently, she's been a one-of in some Temur Energy decks, often in the sideboard. So, while she hasn't enabled decks to succeed in the way that Nissa, Worldwaker once did, she's become a complementary piece of a very good Standard deck archetype.
However, this is only part of her story! As I predicted, Nissa, Vital Force has sneaked into a few Modern decks as a one-of, mostly in the sideboard. One example is this tournament-winning Titan Breach deck. Other decks that have utilized Nissa, Vital Force include Valakut/Scapeshift combo decks and Elves. In Legacy, she's even made the main boards of some competitive Elves decks!
Beyond her obvious utility in Commander, especially in Atraxa, Praetor's Voice decks which can always use and abuse planeswalkers, Nissa, Vital Force has become a competitive role player in not just Standard, but Modern and Legacy, as well! Outside of some Lands decks in Legacy and the occasional Tooth and Nail deck in Modern, Nissa, Worldwaker hasn't built nearly the same resume of competitive playability in non-rotating formats!
So to answer the question of how good is Nissa, Vital Force? She's been a bit better than Nissa, Worldwaker in the long run, and that's saying something!
Yet, Nissa, Vital Force has been available as low as $2.00 apiece! While her price has slowly recovered since then, there's little doubt she's been pretty undervalued.