You are absolutely correct, those legacy boxes probably account for a lot of defficiencies, but if some cableco's can use something more robust than SARA, why can't they all? TWC seems to be going backward at the moment with Navigator, since Passport seems quicker, etc., but it's hard to believe this isn't just because they are trying to standardize their system so they can implement more things in the coming year.
One thing to remember is that the people who are probably most affected, and most vocal, about the switch to Navigator are their DVR customers and that is still a relatively small, but growing, segment. If it's as bad as people say, they are going to have to do some heavy promoting in order to keep customers from switching.
I have the same concerns with 3rd party equipment as you do. There are already enough cableco's saying they don't support SATA expansion, what's to prevent them from saying they also don't support your 3rd party OCAP-compatible tuner/DVR and suggesting that you lease theirs, assuming they will still offer one? Of course, they do support 3rd party cable modems as long as you select one for the authorized list and 3rd party tuner/DVRs could work the same way.
I don't know what Everest Cable offers in KC, but unless it's better than Navigator, I don't know how many people will switch for that reason alone, especially if there is some compensation and a believable promise of fixes involved. I'm sure they've crunched the numbers and have a pretty good idea of what the impact will be.
Many of us have been stuck with SARA from day one so we don't really know what we are missing, but for TWC to step backwards with Navigator in the middle of the game seems somewhat foolish, at least for the short term. We SARA users always have promises of something better coming (when already?) and our only choices are to switch to satellite or shell out $$$ for an S3, so most of simply do the best we can with what we've got.
For some reason there doesn't seem to be anyone from either Lincoln or San Diego posting in this thread. It could be that they are sticking with the local Lincoln and San Diego threads, so you might check those out.