Yes, other people who don't have the font installed won't see it, unless you embed it in images.

Probably. In order for people to see the text in the Gadge font, they would have to have that font installed on their computer. If they do not, everything will be convert to their computer's default font (usually Times New Roman). The only way to "force" an odd font like Gadget on to everyones computer is to convert the text where you want to use it to graphics and then paste them in.

may be an issue for people with dial-up or slow Internet connections, or with people who have the graphics turned off on their browser.