Rogue is a monster of an ally whose stats can often reach 4/4 every turn! You can always trigger her ability by targeting your identity, and in fact this should be preferred to targeting an ally (though Professor X or Nick Fury can afford to take an extra damage). Rogue is also hands down the best X-Men to carry a Protective Training, and in a deck with 3 Game Time she can go absolutely bananas. One of the most exciting cards from Nightcrawler for me and worth using many deck slots to optimize.

There is an alternate use case that Earth Dragon did not touch on in his review. There have been a few ally spam decks I've played where I regularly have all ally slots filled and multiple chump blockers on their last legs. In these situations, Toe to Toe has no downside. I get 5 damage, and open a slot for my next/better ally to hit the field.

Others have all-ready outlined its main function being healing allies so instead I'll note a few of my favorite targets. On Giant Man the 2 healing can equate to 8 damage. Captain Marvel (Signature Ally) gets 4 Thwart or Damage plus 2 card-draw. Wasp gets 6 damage and Goldballs gets 8. When used on Storm (with an applicable side scheme target) this can effectively remove 8 threat.

If you have a mystic identity this card is worth considering. It is has an effective cost of two cards (Played Card + Discard Card) for the benefit of drawing two cards. Because the discard is after the draw phase, it will allow you to cycle and keep cards you want in your hand.

Another interesting addition is that this an "Action" card. This means you could play it in either alter-ego or ego

Others have touched on the value this card provides as free chip damage (in some cases buffing damage to dealt to multiple targets). I also think it’s fairly valuable in a minion killing deck with cards like Into the Fray and No Quarter. In addition to providing extra damage, any excess damage gets converted into either threat removal or card draw both of which are more generally more valuable than damage itself.