I'm spinning up some new servers and I'm tempted to make the leap to 13.04 solely because I can install php5 without a PPA. It's not a big deal, it's just a thought.
I've been using 12.04 for about a year now, it's served me quite well and I learned a lot on it.
I'm not worried about LTS, these servers will probably be replaced with bigger ones, rotated out, re-configured and re-created a few times a year.
I use only the remote shell to control the things, so Unity is a zero factor, I know that's a controversy these days so I figured I'd mention it doesn't matter here.
My stack is nginx, php5, and mongodb. I also use server side v8js in a few small places... if that is of any relevance.
Are there any other differences I should be aware of? My first reaction was "No big deal, newer is better, shouldn't make a difference" - but I can't find a clear answer anywhere that isn't related to UI.
The biggest difference you'll find is the version of packages available for each version. For example, in Ubuntu 12.04, which is an LTS, installing PHP from the official repositories will give you PHP version 5.3.x. However, if you move to 13.04 for example, you'll get version 5.4.x.
You'll encounter situations like that quite often. Even things like MySQL, etckeeper, and quite a few other major packages will have older versions in LTS releases. This is because the LTS release is made and maintained for the type of people that don't want to deal with updates that much, and want to 'set it and (almost) forget it' for a long time. So you want find the latest versions of packages like that.
Other than that, as a developer, you'll find newer versions of various libraries. However, for the common user, this will be a non-factor.
That's really about it though. Ubuntu have not made any recent changes major enough to distinguish 12.04, 12.10, and 13.04 with the operation itself.