BC, some here are not old enough to understand that bit of sarcasm.
http://www.computerhope.com/edlin.htm
True enough
Allow me to flesh out my reasoning. First, Aptana is based on Eclipse. Now, this in itself is not bad- Eclipse is OK, and is probably the best Free Java IDE (IntelliJ takes the top spot overall IMO, but it's commercial). However, Eclipse has many issues on it's own; for me, I deal with them simply because I don't have IntelliJ, just as I would deal with the issues in SharpDevelop if I didn't have Visual Studio- it's better than the alternative of using a Text Editor.
Now I should flesh that last bit out. How is using Eclipse for Java programming better than using a Text Editor? For me, it's the various coding helpers. Eclipse provides a myriad of functionality for code refactoring, inspections, and debugging. You get autocomplete pop-ups, javadocs appear when you type method names, yo uget parameter info, and so on. These are massive boosts to productivity.
Now what about Aptana Studio? It's used for Web development, and primarily aimed at dealing with PHP and Javascript. There is a distinct difference between PHP/Javascript and Java; for one thing, Java is statically typed, and a lot of information about the application can be determined by simply reading the source files. PHP and Javascript, in contrast, are less inspectable. They are dynamic languages and therefore a lot of the application state doesn't even exist until run-time. an IDE for a dynamic language is usually limited to parameter information and syntax highlighting. Which are useful, but just don't provide the massive boost to productivity available from IDEs for statically-typed languages. This presents the additional issue that Aptana Studio is based on Eclipse, which itself is aimed towards Statically typed languages; in some ways it's being made to do something cruel and unusual, like forcing a old monitor into a high resolution mode. So Aptana Studio inherits many of Eclipse's fiobles, and adds it's own to the mix, (like the funny prompt I got after installation that complained I should install git... even though I already had it installed.) In the meantime it's attempting to provide functions and capabilities that simply cannot approach the productivity value that they are aiming for, simply because there is only so much you can actually determine from a piece of dynamic language source code before you encounter the halting problem. And when the biggest advantage is syntax highlighting, well- you can get that with many text editors, too.
(FWIW, I found Aptana Studio's functionality more or less a modern equivalent to Visual InterDev, which wasn't particularly impressive either)