3.0 Haste altered the dynamics of combat in a very significant way. Now some people liked the direction that took them, DMs included, the combat had a swiftness about it that decided the encounter either way. Cinematically, It would have looked something like DBZ which I know people do like.
Otoh, combat without the extra partial action required a player to weigh up and choose their next action with greater care. A spellcaster couldn't buff and attack, a warrior couldn't trip and full attack. Damage dished out couldn't be piled on in a timeframe so short that left no opportunity for healing.
eg: I had the party Cleric get hit with two consequitive cones of cold for 20d6 damage total, killing him. Without haste the opponant could only do a similar 15d6+5d4+5 by investing in 2 extra feats. Instead I used the feats to boost the DC by 4, my bad.
My players stoically handled the above because they desired to get haste items themselves but then later on, in discussion, we agreed that every higher level party they should meet would have haste. One player (rightfully) objected saying that no one 3rd level spell should be the object of such desire and that the previous combat was ok for a deadly "boss fight" but not for the more common battles. I agreed with the sentiment but the haste spell demanded to be cast 1st chance or else one side would be at such a disadvantage, what to do?
Monster encounters over a day in a dungeon weren't really affected as they were there only to wear down the party, haste used here would bite the PC's when the big encounters came. It was only the encounters vs intelligent parties that made the spell really stand out (i.e. when it was used against the party).
In the end we house ruled haste to something similar to revised that someone here at ENWorld posted. I would have compensated anyone that had invested in boots of haste but we restarted campaigns so there wasn't an issue.
