Most are psychology software alternatives to DirectRT, varying in their tradeoff between power and ease of use.
MediaLab is great complement to programs like E-prime, Inquisit, DirectRT and such.
The difference between MediaLab and these other programs is pretty much the same no matter which one you're talking about. MediaLab has more flexbility and greater ease of use with respect to traditional questionnaires (many closed and open-ended question formats) and multi-media stimuli (movies, sound, html, word documents, powerpoint shows, etc.). You can point and click an attractive questionnaire or experiment together really quick and the data files are very easy to work with as they're horizontal (one row per subject) and ready to analyze in Excel or SPSS.
Its weakness is that all the multi-media flexibility requires that it be a traditional windows program so the precision of timing (both display and RTs) is not great. It's also not great when you have a more cognitive/perception type of study where you have hundreds of repeated trials (e.g., priming/lexical decision style tasks).
This is what the RT/precision programs like E-prime, DirectRT, Inquisit etc. are great for. For the latter, it's just a matter of preference, need for elaborate scripting, particular features and such. Those that prefer DirectRT tend to like the simple concept of designing RT sessions in Excel. I wrote it that way because it's what I always dreamed about having in grad school.
That's another plus too, i.e., that these programs were written from a social psych/social cog perspective--which is an unusual find. Although some tasks could be easily done with any of these programs, MediaLab is often a clear preference for users over any program in the "RT" category.
A lot of people use both and embed their precision tasks within a more general MediaLab experiment. In a number of labs, users will embed their Inquisit sessions within a more general level MediaLab experiment--e.g., to administer pre and post test questionnaires and even to control the random assigment of Inquisit IATs and such.
User Reviews of MediaLab and DirectRT
Empirisoft Home Page