FL Studio is the most complete virtual studio currently available. You will be creating wav, mp3 or midi songs or loops only minutes after launching it.
While being easy of access it's an 'all-in-one' audio environment that features multi-track-recording and arrangement, a variable pattern-length step-sequencer with an advanced song arrangement play-list, complete automation tracks, a 64+ track mixer with FX inserts, full VST plug-in support for generators and effects, great in-the-box synthesizers and effect plug-ins, like Poizone or Sytrus or the large and complete FX & sample bank provided. You can record wave from your audio interface or catch MIDI signals right from your favorite controllers and assign them to the VSTs controls. You can easily patch mixer tracks with each other, and almost everything is template-ed/preset-able. The default sampler & synthesizer plug-ins all provide arpegiator and glide functions, a cool delay and granularizer. Advanced audio features may be time-stretching (also known as warping) & beat slicing of samples, BPM detection for samples and so on. I don't really know what it is missing of 'bare features'. One thing that makes it different is just how the interface is. Needed to be acquired like any other, most intuitive, easy, fast and enjoyable once in it. Oh yeah, and the coolest & neatest interface on earth an audio software has is fully skin-able.
FL Studio also provides some functionality for live performance but it might it's major weakness. Other applications maybe more suitable to play live and switch and add patterns on-the-fly, but FL 9 presents some kind if Live mode ;)
It provides much flexibility and presents as an all-in-one "computer instrument" when it comes to composition. Whether you are starting a loop from scratch or want to arrange your whole album, whether you are a crazy looper or a professional engineer, FL Studio will probably fit your needs, making a great deal between instant creativity and pro-level features.