Summary of Findings:
I've never installed Drupal manually before, in the past I've used Fantastico when I want to use Drupal. However, I have installed many webapps.
First user... My Mom - Not very web-savvy
I set the database up for her in my shared hosting's control panel, uploaded Drupal, (and didn't read the INSTALL.php... I think the chmod stuff should be clearer) and showed her the install page. She's making a blog for herself.
First language screen is easy.
Requirements error, directory files is not writable. My mom doesn't really understand FTP, so I'm going to fix the permissions for her and go on.
Files directory should really be included, and the error should have instructions on how to set permissions (or, if you have a reason not to include the files directory, include instructions on the error message on how to create and chmod the directory inside the error. this generic error would throw anyone not familiar with unix permissions off)
It was not clear once I fixed the permissions what to press, possibly make it clearer that you should click try again.
When we got to the database configuration, I told her what the database details were. I think it's a good idea to hide the Advanced section, because in other webapp's installation routine, these settings throw people off. One thing I want to make note of so far, is that I think there should be a Next button at the bottom of each page instead of differently labeled buttons on each step.
The site e-mail step is very confusing for beginning users. The first sentence, about what the E-Mail would be used for, is pretty unclear, and the second sentence about it being the same domain as the site, is not applicable to beginning users. Some text should be included saying that you can use your own E-Mail address if you want, and the text about what it is used for should be simpler.
I think the password verification is slightly too much, it scared my mom enough to make a new password other than the one she normally uses, which is pretty darn secure... A relative random series of letters and numbers.
The 24 hour clock is slightly confusing to us in the States, we are not at all used to it, if you wanted to leave that clock there, how about listing locations, such as Eastern Standard Time for us to make it clearer. Clean URLs is confusing to new users, although she decided to use Enabled which in my opinion is the better options. The Check for updates feature confused my mom as well, especially the part about anonymous usage statistics.
The administration section was slightly complex, she just went right to the create content section. She read the description of pages and stories, and went with a story.
I asked her to change what her site looked like in the administration panel, she started going through admin panels, not sure at all what to do. I think the description of themes isn't quite good enough. Once she got into themes, she figured out how to use it. I think the configure menu, where you change the colors of the site, should be a lot more obvious, because it's an easy way to make the site look cool without messing around much.
Second user... My brother, Evan, age 10 - He's pretty web-savvy, but he doesn't blog or anything
When he first went to the installation site, it gave an error. It threw him off, but he decided to refresh the page, fixing the error.
He chose the English language naturally, and then up popped the files folder error. He doesn't have good knowledge of FTP, so I fixed the error for him. He clicked the help link, but it confused him. He knew to refresh the page, probably from the last error.
Once I fixed the error and we got to the database screen. He got kinda confused, and wanted to put his username and password info into the mysql screen. I filled in the database for him, and we went on.
The Site Name default being Drupal threw him off a bit, he didn't seem to want to change a default setting. I think that field should be blank. He was confused even after I told him it shouldn't be left as Drupal, I think a description of this field would be helpful to users who are not used to setting up webapps. Eventually, he figured out to put in "Evan's blog".
Just like with my mom the email/domain thing was very confusing to him. Unlike my mom however, in the end, he figured he should use his address.
The password thing was also confusing for him, he chose a different password than his normal one because the medium security thing scared him.
And, the -5 time zone confused him, it should be EST or something. He went with the default.
So basically, a lot of the same things as with mom.
Third user... My Dad - He's kinda web savvy, but not a ton
As before, the installation site had an error which threw him off, and he didn't know what to do. Once I refreshed the page, it got rid of the error.
He chose English, then he saw the files folder error. Once he was really confused, I fixed it via FTP. He clicked the help link, but it confused him. He knew to refresh the page, probably from the last error.
He, like Evan, thought that since the default site name was Drupal, he shouldn't change... Don't set a default for a field if you expect people to change it! Site E-Mail address confused him, he eventually decided to put in his own.
Administrator account was fine...
In the admin panel, he thought that there were too many options, it confused him. I had asked him to figure out how to "change the way your site looks", and he got a bit confused because there were so many options. He looked through the options in the site building category, and first started in the first option, blocks. Once I told him that blocks wasn't right, he found themes and went there.