As for prefs, it's always better to expose as many prefs as possible via the prefs UI in addition to using about:config. SeaMonkey seems to be more of a techie-oriented browser than Firefox and as a senior software engineer I appreciate this. SeaMonkey should always allow users to choose how they do things and never force users to use a particular way. These are two areas where Firefox fails miserably, it seems the Firefox people are catering to the lowest common denominator with their simplistic prefs UI and forcing major UI changes like the awfulbar upon people despite numerous complaints is just wrong. Worse they appear to simply not care about user choice, a perfect example is bug 407836 where they removed a pref to change the urlbar dropdown appearance for no reason at all. Manually reverting this patch restores the pref and works just fine (I tested this with Firefox 3.0.3). The SeaMonkey devs should never go down the path of not listening to its users.
Also does SeaMonkey need to copy everything from Firefox and Thunderbird ? Obviously the Mozilla people control Gecko and the backend toolkit but SeaMonkey shouldn't simply be an integrated version of Firefox and Thunderbird, it should be its own entity. Copying things like the awfulbar without prefs to get the existing urlbar behavior, its frecency algorithm, combined back/forward button, any of Firefox over-simplified pref UI, the places system, bookmarks manager, download manager, etc. are a cause for concern for SeaMonkey users who don't like these features or don't see the benefit of them. Remember many SeaMonkey users probably like the way things are and may not want Firefox's way of doing things.
The biggest problem I see with SeaMonkey is that its always behind Firefox and Thunderbird. Firefox 3 is already on Gecko 1.9.0 while the release version of SeaMonkey is on 1.8.1. SeaMonkey 2.0 which uses Gecko 1.9.1 will likely come out months after Firefox 3.1 does (which is slated for the end of the year). Is there any way to close the gap ?
Finally has the SeaMonkey council considered some sort of campaign to increase SeaMonkey's profile ? I've found that while most people know of Firefox, few know anything about SeaMonkey.