(This was just going to be a comment, but it was too difficult to write all of it in the little comments box, I kept having to scroll, etc. So it's now a full post.)

Yes! pros and cons lists are awesome.
Especially this one. Here are my responses to each pro/con.
1. Yes, this is true. For most. Except, I had to go pick up some checks for Aaron at the temp agency he was working at for a while and his recruiter couldn't pronounce his last name if her life depended on it..."Jarbru? Yarbrat?" And she knew it was wrong too...her confused look was priceless.
2./3. It's McMillan that's Scottish. Yarbrough is just plain...white? But these two make me regret even more (bc I had already thought of it) that I can't change the name to McMillan and claim Scottishness.
4. Actually, I never thought I would mind, but this is one of the things I worry about. For the rest of my life, I will have to depend on my skin color to determine my race.
Cons: Hilarious. I can deal with 1./2. because Y isn't that far from T.
And, I have this theory that many people's lives have changed due to the placement of their last name alphabetically--all my close friends have last names in the R-Z part of the alphabet, all due to homeroom placements in middle school. Sometimes, I wonder about all the people I would've been amazing friends with in the A-R range of the alphabet, but other times, I surmise that A-R people are wholly and entirely different from myself and therefore I wouldn't have got along with them anyways.
In any case, the point is, according to this theory, Y isn't far enough from T that I won't still be in the same alphabet bracket and therefore I will not change my fate too much in changing it.
3. Yes! This would be sort of annoying. Some of the tests I take now are barcoded with my identity though, so that will make this an easier transition.
4. This one is a doozy. If either of us gets famous for writing a Great American Novel or some such, we must be sure to mention the other on an Oprah interview, so the relation is made known. Just throw it in there casually, as such:
"Well, Oprah, you know my sister (her last name is Yarbrough now, but she IS my blood relation) was really at least 80% of my inspiration when I wrote this book that you are now recommending for your book club. As a side note, I am so honored to be a part of this elite group of authors that includes Gabriel Garcia Marquez!"

Mr. J- I agree with you about the hyphenated last names. It feels sort of unforgiving, and overly inconvenient--now, not only do both parties have to change their last name, they both have ridiculously long ones to sign. And then, in addition to just being a last name, the hyphenateds become sort of too significant...somehow stating a political/societal stance as well as just being a name. Too much work for just a little hyphen.

Elissa- If you could've chosen, what would you have liked to change your name to? As I said before, I think McMillan sounds quite distinguished. Would it have been British? Kensington, perhaps. Or maybe a distinctive Indian name. Guntapalli?? Ok that was a joke. You remember Bharath, right? Lol. I sure dodged a bullet on that one.
I think it could've been worse though. Your Aaron's last name could've been Tittsworth, or Dickey, or...a whole other slew of possibilities. But! you have to promise to own up to it, pronounce it clearly and succinctly as you shake the other party's hand: "Hello, my name is Ellissa Ball-MAN!" No slurring, or un-emphasizing it. : )

In any case, yesterday I started practicing signatures in response to your comment, Rachel, while I was studying and felt like I had effectively regressed 12 years in age.
It will be quite wierd to change it. I wonder if credit card places will really even notice if I just sign keep signing my original messy signature despite the fact that the actual name has changed. Probably not. Actually, they probably wouldn't even notice if I started scrawling an 'X' in place of a signature.

So, to bring closure to this discussion, I'm definitely going to change my name, I guess I was just feeling a bit nostalgic about mine. I like it, it has served me well, and it will continue to serve me well as a middle name (I don't have one now, so I will keep my last as my middle, the way my mom did it).