Yeah, there are so many layers to it, it's always hard for me to respond to something like that.
After a loooong break, a decent amount up my nose, after a minute, will give me a sweaty heart pumping sit down a second feeling that lasts five minutes. Is that the rush? Mostly uncomfortable for me. (No, I don't bring a scale with me to know my bump sizes)
Then there's a jazzed, upbeat feeling that lasts maybe half-an-hour. During that time your thoughts will flow in circles, usually merrily. You'll be social, but best not to talk to anyone.
Then the sun sets, your thoughts get more concrete, your body a little stiffer. This is the productive time, if you can avoid the call of pr0n. Let your mind find whole new concepts, find some new connections, decode random emails, take apart a VCR, try new brands of gum. This can last for several hours. Safe to talk to people, but you don't want to.
Then comes the night, and insomnia, dragging reluctantly into morning. (ALthough usually you need a couple more bumps to stay up all night.) Breakfast is unpalatable and served with a sense of impending doom and horror. Every drop of moisture is gone from your body. You see things in the carpet. What is that anyway? Did I drop a shard . . . this will last all day.
Change the curve shape slightly, to be steeper, and that's your generic smoking profile. Although smoking is the most variable of all the ROAs: I'm pretty sure I could fit a n00bs bowl that takes ten minutes to smoke, up my nose in ten seconds.
You can also dissolve a massive dose in water and squirt it up your butthole. It can take over ten minutes to hit (you really do need to have a recent vacancy in your rectum), but is said to feel closer to IV than anything else. Course, an IV user would be coming down already, riding away on your bicycle.