How much text is too much?

When developing a site, how much text is too much? When will a user stop reading? Specifically, I am developing a Web design/development company website, but unfortunately I am not a marketing guru. We are trying to develop the content, and one approach is to have a 500 word essay on why we are the best, and why you need a web presence, or we could just have a couple of sentences with bullet points. The hard part is getting the point across without being long-winded and loosing the reader. What would you consider the limit, the point where a potential client says "f*** it, too much to read" and moves on to another site? Are there any studies done on this, or any general rules to follow? What is your opinion?

replying to your title your description is too much didn't read past second line

I'd say it depends on how interesting the material is, and how much the person reading wants the information.
For instance, I'll read tutorials online that span 8 pages or so. But I'm not going to read the same amount of information about somebody's poodle (unless it's really funny).
You might take a tip from the newspaper industry. The first paragraph of a story contains all the critical information. Everything passed that point fills out the content in decreasing order of importance. You make you first paragraph fit on one screenful, and try to make it interesting enough to engage readers further.

I hate to say this, but imagine you are creating PowerPoint slides.

You really should only have a few ideas per page, and not more than one screen-full of text. If you've got a scroll-bar, you've got too much.

Now with that said, I think it is time to pretend that everybody is viewing Web pages at 1024x768 or better. Personally I'm tired of seeing sites built for 640x480 glued to the top left corner of my 1280x1024 monitor.

I don't know about that. Powerpoint slides are designed to emphasize an oral presentation, not as standalone content. A handful of bullet points leave a lot to be desired when it comes to getting actual information. They're supposed to be a summary, not the full content.
That being said, I've read several studies that say the majority of users won't scroll for more than two screens of text. The same studies say that more users scroll than click on links to the next page of the article, though.
From personal experience it really comes down the quality and applicability of the information. You're writing brochure-ware, so chances are you're not going to get people looking for a thorough tritise on the bottom-line benefits of having a website versus the capital output yadda yadda yadda. Stick with the bullet points. Try to impress the client that the development company is competent and worth their time. You can always include the essay as link to "expert commentary about online commerce by one of our talented web guru's".

Pictures. I like pictures. lol