Ok, I've had some time to cool off and think some more about the Star Trek "Special Editions"...
I suppose alot of my negative opinion of the tweaking stems from the fear of them screwing it up, much like the Star Wars Special Editions (which I find unwatchable)..
What I think will happen is they will replace the space stuff with "improved" visuals. However, the rest of the show is going to still remain dated and, at times, very low budget like the alien planets (often times a white backdrop colored by lights). So the next step, following their intent to improve/update the visuals, would then be to replace the skies and possibly some of the sets. So almost everything outside of the actual actors would then need to be replaced/enhanced - a huge, difficult task. Then you run into the aliens, which are rubber suits or optical effects... so are they then to be replaced with digital counterparts?
In addition, putting in new footage/fx would have to stay true to the original look, feel and design. The show Enterprise suffered from this, I feel. It was supposed to be set before the original series, but the look and designs did not fin in at all. If anything, it looked more advanced. The live action (actors) footage screams of the 60s and I don't think you can get beyond that (or would I want it to).
If they DID go in and do complete new set replacements and brought the low budget tv show more towards today's standards and looks AND did it well, then I suppose on a new level, it could be very cool. However, the quality would need to be spot on. It'd be a shame if they simply replaced cheap looking practical with cheap looking digital. Being the jaded pessimist that I am, my money goes to seeing cheap digital. The use of CG opens another possible hurdle - the quality of CG & compositing changes on a yearly basis, sometimes even monthly. What looks cutting edge one year may look outdated the next. This isn't always the case, but it happens more often than you'd think. ST: Next Generation is a good example. When it was on TV, I thought at the time the space stuff was incredible looking. If you look at it now, it looks more like out-of-the-box CG. Technology and techniques have changed and improved since. So in order to have a better lasting screen life, the studio would need to spend the money on a facility that could an absolute great job. It being television, I don't see that happening.
Trek was always very much The Stage brought to the screen (especially with Shatner's presence). Atleast that's how I viewed and enjoyed it - that was part of the charm. In the end, I say don't risk messing it up. Preserve what was done before. I'd hate it if they went back and replaced the 1933 King Kong with CG.....