My opinion
Since this particular thread has gone on for several pages and shows no sign of slowing down, this opinion will most likely be buried. And since it is past the 6th page, it is not too likely to be read by many. So be it.
My definition of an over powered ANYTHING is as follows:
Lets say you are going into a fight that is at least EQUAL in power to your party.
As an Attacker:
Would you always (95% of the time or more) choose to cast Haste at the expense of other viable options?
As a Defender:
Do you find it worth while to use time and / or resources to prepare a defense specifically against Haste at the expense of other strategic and tactical considerations?
If a typical party finds its self about to fight a Large Dragon, an identical hostile party, or other difficult foe, they will probably feel compelled to cast or use Haste. If they want to cast a single target buff spell, there are many choices. Blink, StoneSkin, Fire Shield, Improved Invisibility, or Mirror Image. All are likely to be useful in a variety of circumstances. They could also choose instead ot attack. Fireball, Lightning Bolt, Ice Storm, and Enervation are all powerful attacks. But Haste is simply more useful then all of those.
As a Defender, someone could choose to either use spells or items to gain elemental resistance, protection against summoned creatures, protection from melee attacks, protection from ranged attacks, or a form of escape. Dispel Magic is truly a great spell, but are you taking to cancel a StoneSkin? Are you trying to remove Mirror Image and Blink? Or are you most afraid of an opponent using Haste?
For me, the answer to the first question at least is yes. I cannot think of any circumstances where using Haste is a bad idea. As a chosen action, its potential benefits out do all other actions I can think of. I can think of no other 3rd level spell that is as helpful to cast. I can think of no other magical effect that is as useful for a similar cost.
As for the second question, the answer is almost a Yes. If you know your opponent is going to use Haste, you will want to counter it before most other considerations. But most tactics that work against Haste are also effective for other considerations as well. Slow is a great spell to cast anyway. Against melee attackers, it is crippling. Dispel Magic will take down more then just Haste. Haste also has a reasonably short duration, and if you can keep the party from attacking you for the duration. Throwing a few Wall spells between you and the hasted opponents can keep you safe long enough. Turning Invisible and waiting the spell out will work as well. You can also just enter a Rope Trick and consume some healing items / spells. Parties of Humanoids can just take Run actions and scatter to minimize casualties.
The spell is not broken to the point of being game breaking, but it is way too useful for a 3rd level spell with an easily found component. StoneSkin is arguably more useful, but it costs 250 gp per casting, and is 4th level. I dont mind it being a 3rd leve spell, but I think it should at least have a costly component requirement.
END COMMUNICATION