you just insulted Bing! Why? I actually use it a lot, because even though it's not quite as fast and minimalist as Google, I do NOT trust Google!!! (Except for that my phone has Android but oh well lol)...
Google's spiders are much more active at crawling websites. If you notice your "Who's Online" page, you'll probably see that the GoogleBot is there much more often than Yahoo or Bing. Also, Google probably has more power to process crawled pages, so they can get new sites into their results that much faster.
A counterargument to a website indexing quickly is that they're more likely to include a newly-created spam site in their search results.
Just keep doing what you're doing. The other search engines will find you. In my opinion, the other search engines don't have the refined algorithm that Google has, so if you focus on SEO for Google, it will take care of the rest of the major search engines. Of course I believe you could do things to rank higher in other search engines where you would rank lower in Google, but that's another story.