i'll add to that, that for service work purposes, siemens had one of the greatest covers of all time. The cover was/is hinged. Remove 3 screws and hinge the cover open, you don't even have to remove the cover. Let's you get into the guts and troubleshoot very easily.
For resi: I would say blind or SOSS hinged, and pop latched with a corner bead to blend it right into any wall. I am totally sick of discussing where it can and can not go with people who outa know better by now.
For Comm: Hinged on hinged, but with a set of screws you could transfer to also include the breaker dead front as well. Just move them over one by one for what exposure you want. Dead front on - dead front off. With it on you cant work on anything but the Gnd and Gnded bars, you need to get past the dead front to access the breakers....
Enough of covers.... Get rid of K/O's on panels I am sick and tired of them! For all the extra time I have wasted trying to gently remove one without taking out the rest, I could make my own in less time... Or just plain not being where I need them. Another waste of time. If you're installing a panel, and don't own a KO set - you have no buisiness doing it in the first place IMO. I know there are some available without them, but are fewer and farther between on availabily these days - and non-existant in many brands.
Another would be the logical placement of grounds and neutrals. One of each on each side for AF's and GF's.
Mark Heller "Well - I oughta....." -Jackie Gleason
e57 brings up an interesting point about the AFCIs and GFCIs needing a neutral bus near every breaker. It's looking fairly certain that the 2008 NEC is going to be implimenting a requirement for more, if not all, circuits in residential panels to be AFCI protected (as I understand it thus far).
This means that we're probably going to see most, if not all, of the panel manufacturers redesigning (or at least modifying) their products to accmodate the new requirement.
This might be a good time to start lobbying the manufacturers to make the changes we would all like to see, such as some of the great ideas on this thread.