The action scenes in the special were pretty great, just a lot of nitpicks on the story.
Them not being able to get the original (living) rangers was pretty obvious at the beginning and they didn't seem to grab the cleanest audio to use when dubbing them in.
They kept leaving the monsters in the heart of downtown during attacks. Kill the putty's, move civilians 5 feet off screen and leave. This wasn't punished by the monsters just resuming their attack and bringing the Rangers back.
Kid Trini "We really need to kill the monsters instead of incapacitating them." Billy "This is the plan" 5 minutes later, "we need to kill the monsters"
Alpha: "I made these backup power coins, but it will put you in the situation of too much Red and too much Pink power" This is never brought up again.
Ignoring the Zeo powers and possibly the Turbo powers. (Turbo powers are kind of hazy if they can morph or not. Justin got his powers back briefly during In Space, so they still exist)
Speaking of destroyed powers: All the original power coins were destroyed. They were replaced with the Zeo Crystals (Which weren't destroyed, just abandoned for the Turbo powers), which were superior in every way.
All of the nitpicks aside, the nostalgia factor was a solid 8/10. The Adam/Aiesha cameo's were a bit forced since they gave them nothing to do. (We can tell who let themselves go in the 30 years.)
I'm just old and don't like inconsistency of my spandex wearing heroes.