I don't like the idea of practically every unit having some ability. I'd really hate for it to become WC3.
Actually they don't. This is one thing I was very resentful against with starcraft II until I really went through the Unit list and there aren't that many abilities. Zerg for the most part have only two ground unit with any abilities other than burrow.
Terrans have the same abilities for the most part on their ground units, with the exception of the the ghost whose abilities are all changed. Mauraders, Jackals, and Thor don't have abilities, Reapers have mines like the vultures, and Tanks are pretty much the same, with no medics or firebats, marines are the only ones with stim packs.
Banshees have cloak like Wraith, and the Nomad is basically the science vessel. Viking's Ability is just the fact it changes between two units, and Battlcruiser still has the same ability, or the chance to swap for a different one. Dropship has merged with the medi alright, but in doing so it just swapped the abilty from the one unit to the air unit. not a big deal, and it is auto heal anyways. In comparison, amongst air units only Battlecrusier has gotten any sort of new ability, but you have to sacrifice it's original to use it.
Protoss granted gave Zealots charge, and split the dragoon to two units, one with blink and hardened shield. All things considered the Immortal's and Zealots abilities are passive, so I don't see how it is much more of a deal than having speed or sight upgrades from starcraft. Plus the DT, Colossus, and Archon all lack abilities, and the High Templar and Nullifier are the sole spell casters for ground units.
Carrier, warpray and Observer don't have abilities, and the Mothership replaces the Arbiter as the air caster, with the Pheonix as a Scout/Corsiar hybrid with one abilty like the corsair.
I'm pretty happy with the ability distribution amongst units personally.