There is absolutely nothing wrong with Fidelity as long as you stick with their low cost index funds, and avoid paying for management (they have professional management that for a ~0.50-1% fee, will do all the scutwork on your portfolio - but it's unnecessary if you do a little basic research).
They have comparable funds to pretty much all Vanguard funds, have excellent (free) customer service, a better website (in my and many others' opinion) and lots more perks than Vanguard since they are a for-profit company.
https://www.bogleheads.org/wiki/FidelityFido has been changing the Spartan series of index funds over to be just "Fidelity" so check tickers to match up if there is any question about getting the correct fund.
Think of using Fido (if you are an index investor) as being the type of person that has a great rewards card and never carries a balance so the card company don't earn the high interest (management) fees off you, just the little transaction (expense ratio) fees. We're not their target audience really since index investing doesn't net them as big a profit, but they'll still treat us well since we're customers all the same. They offer index funds as a loss leader, hoping that you'll start dabbling in some of their management funds, but no one is going to pressure you to do so.