When I think about this issue, I think of it more of a nice to have usability feature. I would love to have this but I can see that Evernote is NOT a programmer code snippet tool.
I think what would really shine in this app is the use of markdown like features to designate the language for highlighting. For instance, using the 3 back ticks with a language type at the end of the three ticks as a special built in function of EN that applies the syntax highlighting within that block only and keeps your spacing indentation foreach newline, only within that block. For example:
my code block
That would be really nice. As a programmer, I honestly don't use Evernote to keep track of my code. HOWEVER, I use it extensively for my note-taking, I use penultimate extensively for my mathematics. I use notebooks, tags, all the nice features that EN has. I do like the code block tool but now that I'm getting knee deep into some new books that include code, I'm suddenly finding myself in a position where I want to keep notes on the new things I'm learning within new languages I'm picking up as I learn a topic (like statistics and R). Honestly, I would really like the code highlight feature when I'm learning new stuff from books. That's where I see this feature in most demand for people like me. Not as a code snippet tool, but to keep notes on the code I'm writing as I learn something new, or to annotate code blocks and write notes around them, like a design pattern in C# or the strange ~ operator in R that recently made me go "huh?". I would want to have the code block highlighted and write in notes both in comment form in the block and in notes before and after the code block. I can easily see myself doing this a lot.
Other than that, if a programmer is sitting here wanting to catalog their code snippets, I wouldn't recommend EN to do that at all. It's the wrong tool for the job in my opinion. Honestly I don't NEED this functionality of code highlighting, but it sure would be a nice feature for me.