Stormpulse was politely turned down by YC in 2007. I'm sure getting accepted would have changed things in a good way, but I can't complain about the way things are going; a YC-no-thanks is not a fatal judgment.
The SWF is something we wrote ourselves, but all of the sources/images/layers are public info. For example, you can download the base imagery from NASA here: http://earthobservatory.nasa.gov/Newsroom/BlueMarble/
As far as B2B, I haven't seen any negative responses there either, perhaps because we don't deal with many middle-management MBA-types. Most of the fans we've heard from are either low on the totem pole, helping us get in the door at their mother ship, or so high on the totem pole that @stormpulse.com might make them think of us as a large cockroach at best.
For example, if gmail were to no longer be the preferred email address system of techies (because they start charging, they are no longer reliable, or as seen more recently, you get totally locked out with no way of getting real support, etc), you would have to struggle with letting the word out about your new email address, or something.
With your own email address, you would have the flexibility to switch out to a different mail provider with your domain's MX records. You also can print business cards without worrying about reprints and the like. :)
Anyway, I don't necessarily think bigger customers will think you're bigger just because you own a @stormpulse.com email address.
Yes I know it is 'nice' to have your own domain-based email accounts, especially when trying to advertise your domain, but all the advantages of gmail encouraged me to switch and I've never been happier.
I use GMail on my own domain.