The main thing I look for with FizzBuzz solutions in general is how many modulus operators are used. The junior end of the spectrum tends to use four (% 5 && % 3; % 5; % 3), while intermediate/seasoned developers will either use three (% 15; % 5; % 3), or two (storing % 5 and % 3 in variables, then comparing the combinations).

My personal preference in terms of demonstrating maintainable code is using two modulus operations with variables. However, I fully understand the argument that an additional % 15 is preferable compared to the overhead of storing two variables on each iteration. Both are valid approaches IMO, and the debate can roar on for eternity. Micro-optimizations and whatnot.

I just don't like to see four modulus operations, which IMO shows a lack of basic willingness or ability to refactor while coding. It's fine to initially write the four modulus operations, but if someone doesn't immediately catch the duplication and do something about it, it screams "I write code until it works and then move on without cleaning anything up."

Strangely enough, only once have I seen someone use the % 15 optimization and add a short comment along the lines of "// least common multiple, divisible by both 3 and 5". Spotting the optimization is nice; placing a short comment explaining why % 15 when the test is about % 5 and % 3 is a nice touch. Explains something that might not be immediately obvious to the next person coming to the code.

Aside: it astounds me how many people, when asked to write a short snippet of code during an interview, have basic formatting problems and inconsistent code style. I've seen two lines of code inside an if() block indented at different levels, with no excuse for "different opinions on formatting". Not a wrapped line continued on the next, but just two simple statements inexcusably indented at say 8 and 12 spaces. Don't call us, we'll call you...