A very mixed bag. There are some new changes that are very well done, while others feel very out of place and, despite their best efforts, look too much like CGI.
One of the lower points in the remastering effort was in "The Doomsday Machine" episode. The work done on the actual Doomsday Machine itself was ill-advised since the effects team removed all traces of transparency. Michael Okuda justified this change by saying the transparent look of the Doomsday Machine was mistake done by shoddy visual effects work at the time. As someone who admires visual effects both old and new, I think this was a big misstep since a lot of visual effects seem to benefit from unforeseen consequences like this. Having the Doomsday Machine show a bit of transparency is not cheesy in the slightest since some of the most hardest materials known on this Earth are transparent. Even Kirk says that Diamonds are the hardest substance in the galaxy (Apologies to Cast rodinium). Daren Dochterman, a visual effects artist who worked on Star Trek: The Motion Picture Director's Edition did his own take of the Doomsday Machine with the transparency intact.
Another mixed bag was the visual effects team using elements from other Star Trek series to connect into this one. A good example of changing something that fits in with other Star Treks was replacing the stock "Botany Bay" footage from "The Ultimate Computer" and using a new model based off of the transport ship from the Animated Series. Nice continuity connection to a pretty underrated series. A bad example of changing things to fit with something is what the team did to the Tholian ships. Just look at it.
The original ship seen on the left had a very simple 'crystal' look to it with multi-colored lighting sources to distinguish some of it's areas. It was cool, different and above all, alien. This newer Tholian ship just looks like they took the basic shape of the design and just threw on typical ship elements like a metal hull, fins, and more edges. The Web itself also looks bad by comparison. Obviously this was done to keep it in tone with what the Tholian ships looked like in Enterprise, but even there I thought it was a mistake.
The work that I thought really benefited the episodes are the ones that actually helped tell the story. The two episodes that do this are "Amok Time" and "Court Martial". In Amok Time, some of the static shots of the Vulcan courtyard have been replaced with long establishing shots to better showcase the actual location. The new matte shots really fit in well with the rest of the live footage shots and really helps sell the fact that Vulcan is an alien world with harsh red skies and orange terrain.
For Court Martial, we not only get to see where that pod was located on the hull of the Enterprise, but the effects team also took the extra step in weathering up the Enterprise to make it look like the time spent in the Ion Storm was not a cozy ride. The added Constitution starship below the Enterprise that looks much more cleaner was an excellent touch as well.
