Senses
Vision pulsates, oscillates. I'm hyper aware of visual noise. The colors and image afterburns normally seen with the eyes closed are overlayed with eyes open. Eyes closed I see... patterns.
Audio is stretched. Longer in duration, as well as more detailed. I'm able to understand what the fuck people are actually saying in music (Modest Mouse is a prime example) and the intricacies of music are enjoyed. The first time I listened to Jimi Hendrix "Castles Made of Sand" I almost died when the solo started. I could really appreciate the song (especially its mix), and was blown away by it.
Tactile sensations pulsate much like vision. This is most apparent in areas that are dense in nerve endings. Putting my hands in my pockets to retrieve something feels very choppy.
Taste and smell are magnified in the best of ways. Everything becomes palatable, more detailed, and significantly more gratifying. Pizza ftw. Sushi is brainfucktastic.
Sex is about 10 times better, although I never really enjoyed sex to begin with. Never had an orgasm, and the "feel good" feeling is fleeting.
Interpretation
Movies are much more enjoyable. Seem to be "deeper", with greater entertainment value.
Special effects look ridiculously cheesy. A relatively recent movie will bear the resemblance of special effects used 30 years ago.
Music is better, as said before. In fact, everything's better while stoned. Well, not everything, but anything that is already intrinsically enjoyable.
Other perceptions
Short term memory diminishes, especially at high doses. Disassociating.
Everything has a greater significance. More elaborate.
Everything is funnier. The line "cough, it'll make you like ten times higher" in Pineapple Express almost killed me.
Thought can be more closely examined.
Thought pattern is perceived to be different. Wild conclusions to be had. Paired with anxiety, can create paranoia.
Time dilation.
General relaxation. Floating. Fun.
EDIT: Forgot the most important thing! It feels like I'm in a video game with terrible frame-rate! About 10fps, subjectively.