The remastered effects seem to be tastefully done. What I mean is they don't try to really deviate from that original broadcast, trying to keep in spirit of the limitations, trying to just show a better effect, not trying to make something wildly new (though we got more variation for the planets, like Mudd's spectacular planet). We don't get whole battles made up from nothing basically.
Agreed, and I think this is the strength of the remastered effects. They're very sympathetic to the originals for the most part. There's one sequence where the planet killer attacks the Enterprise in "The Doomsday Machine" where the ship basically has the physics of a physical model, ie it tilts as though it's an actual optical effect. Don't know why that particular shot sticks in mind but I liked it when I saw it, made me feel like the SFX guys were well aware of how important it was not to fiddle about with them too
Having said that, there are some moments where I definitely prefered the tactile feel of the original model work, like the sky shots of the Enterprise in "Tomorrow is Yesterday". And while it's kinda cool to actually see Klingon ships in "Errand of Mercy", it does feel like history has been meddled with a bit, given we all know the Klingon ship didn't really debut on screen till season three.
On the whole though I like both sets of effects, but have no hesitation in giving the remastered versions the tick of approval.