Tomkel: Has anyone played it all the way through?
Does it have any redeeming qualities?
Is it as bad as everyone says it is?
Yes, several times.
Yes, but it depends a lot on what you are looking for. MOO3 allows for a lot of micro-management and is quite detailed, so control freaks might enjoy it.
No, but it is highly flawed. The AI is terrible, navigating the menus can be really annoying (far too many sub-menus), some things don't work (or at least does not seem to work) and the amount of micro-management can get really tedious. You can automate things (there is even a built in way to "program" the AI to build things in the right order), but even then the AI can decide to do stupid things, like only building recreational centers all over the planet, so you need to keep constant check on it.
If you intend to play it, make sure to mod it. That way you'll at least alleviate some of the flaws.