I often wonder what the average passenger thinks when they see it, and perhaps notice they are boarding it. I wonder if the wonder if they are on a UNITED airplane or not, or if they really "get" the intent: an ad for Star Alliance if it communicates to them that Star Alliance is a strong alliance and benefits them. Perhaps FF who have high status on a *A airline.
I remember reading some time ago that an elderly man refused to get on a US Airways flight because the plane was in Star colors and didn't say "US Airways" on the side. He didn't feel comfortable getting on a plane that didn't look like it was operated by US, and that's what he paid for. Supposedly he was reaccommodated on a later flight. Obviously this is a more extreme case, and it could be embellished in the typical FlyerTalk fashion, but it is amusing to think about.
EDIT: Ah yes! Here's the thread: viewtopic.php?t=456373
I would be willing to bet that if you were to survey the flying public (i.e. non-elites, non-A-net posters, non-FlyerTalkers), name recognition of the big three alliances themselves probably isn't very high at all. But I think most fliers who travel on overseas tickets every now and then have at least some rudimentary understanding that their home airline of choice (e.g. UA) has partnerships with other airlines to get them to destinations their home airline doesn't serve and that they can earn miles for it.
The alliances have facilitated more codesharing across the world, yes, and they have made it easier for regular passengers to build more complex global itineraries and to receive FFP benefits, but I think we've reached the point that alliances just aren't as powerful as they used to be in light of more closer JV/ATI partnerships.
As for the brand itself, I actually really like Star's look. The black and white looks very powerful and striking, and I think it was smart of Pentagram to stick to all neutral colors for a brand that has to wrap around 20+ other airline brands. I really like the SkyTeam mark too, but the livery just looks wrong to me, and oneworld's just looks half-assed.