Personally I think they do a difficult job well, but that doesn't mean they are perfect, just that imo they are doing the best they can in very difficult circumstances.
I think if we are to improve on the present situation, some form of accountability is required. Maybe a review or appeals committee that looks into the more controversial decisions.
As with football referees or even policemen, there need to be some element of independance to any such committee. Maybe it could be headed by Supersub, with JBG and Bigmick (both former successful MOD's and probably as well respected as any on the site) making up the team. Perhaps even an additional member who could be appointed on a monthly basis, to give everyone a chance and bring a feeling of collective responsibility.
This could lead to numerous frivolous appeals etc, so I think it should really be restricted to bannings (sin-binning) and multiple cardings, and not for deleted posts (sorry Kharhaz) thread lockings, single card etc etc.
The second problem is it may put Mod's off doing their job properly if they feel their actions are going to be constantly questioned. They may decide its easier to ignore or just card someone rather than take the appropriate action of banning someone who deserves it.
I feel this could be addressed by restricting all inital bans to 48 hours until reviewed or ok'd by at least one member of the committee, and only then a time limit added to the ban. (If the ban was harsh 2 days wont kill anyone)
A slightly more controversial idea might be to restrict the appeals/review process to established members only. Newbies, people with less than 6 months posting and with say less than 200 posts being probationary and not covered by the appeals process?
People with 13100 or more posts and who's user name has a @ in it should obviously be exempt from any bans.

This is not intended as a Mod knocking opportunity, but as a genuine attempt to improve the site. Hopefully while my ideas are no doubt unworkable and implausable if explored fully,others may have better and easier solutions.
If nothing else, some form of appeals proccess should be inplace in my view. The current method of voicing disapproval by starting a thread has obvious disadvantages, as the point often gets lost in a sea of personal responses.