Speaking of constructed, what are you going to play in a RDW deck that doesn't have haste?
If we're talking limited, then you're spending one extra mana in order to give a creature haste. Assuming your deck has a good curve, if playing 2CC creature on T2, then swinging on T3 is the same as playing this on T2, playing a 2CC creature on T3, equipping, then swinging. Of course, in the late game these rings will win the game but they all do that, not just the red ring.
The only time I see the red ring really being useful is when you're sitting around with a bunch of mana and top decking. Getting in a swing one turn earlier than you would otherwise could mean the difference between a victory and a loss, but that's a pretty fringe situation.
If we're talking limited, then you're spending one extra mana in order to give a creature haste. Assuming your deck has a good curve, if playing 2CC creature on T2, then swinging on T3 is the same as playing this on T2, playing a 2CC creature on T3, equipping, then swinging. Of course, in the late game these rings will win the game but they all do that, not just the red ring.
The only time I see the red ring really being useful is when you're sitting around with a bunch of mana and top decking. Getting in a swing one turn earlier than you would otherwise could mean the difference between a victory and a loss, but that's a pretty fringe situation.