Yes, IV Cat ... is ... the cat's meow ... so to speak. I would say it is probably alot more common and popular that you might think. I always hated sniffing cat. I hated the smell and taste, and the stuff I had burned like hell. Most people I know would prefer to IV it compared to other routes. Probably the most intense rush/experience I can think of standing on its own. It's up there with IV cocaine as far as intensity, but much more so, I think, plus it lasts a bit longer, so even better... you can settle into it and enjoy it. It is good for two shots before 'the magic' goes away and it is just stimulating. In other words, tolerance is quickly gained. For about 30 minutes after your shot you'll be higher than a mofo, you'll have visual distortion at higher doses (.25g and up) .3-.4 is a really good dose, any more and you're really in it to win it. Have some cold water nearby for drinking and splashing on your head, maybe (I like to do that) - I get so hot the water starts evaporating off of me and I got steam coming off my head.
Anyway, after about 30 mins you'll start coming down and you'll probably want to redose around then if you can. You'll still be high for an hour or two after the initial rush, but it tapers off, and sleep can be achieved not too long afterwards, hopefully. The come down isnt TOO bad, not as bad as coke IMO. Really helps to have some landing gear. An opiate, a benzo, maybe even some kind of tranquilizer - seroquel (quetiapine) and zyprexa (olanzipine) work wonders for killing the crash and anxiety and make for a great experience.
I have noticed in the past that if I did cocaine a few days leading up to using cat, especially IV, the experience was significantly diminished. Some might even think they got sold bunk drugs or it just wasn't that good. I IV'ed cat once or twice before I got the REAL full-on experience, and it was a big difference. So if you can, give yourself a break leading up to cat use if you can, and pass that advice on to anyone thinking of using cat. It is almost like an MDMA experience. You want to make sure your brain is nice and fresh and charged and ready to be flooded with magic. Otherwise, it doesn't live up to its full potential and it is just kind of a waste.
If you are going to IV, you don't "send it home" until you know you're in that vein good. Get a nice flag/register, and test it by drawing blood in, if it floods in ... then slam that shit and hold on for dear life! It isn't something you want to take your time with and do slowly. The last thing you want to do is hit half of it and then have to fumble around trying to get a register again. Know your dose, find it and just send that mutha fucka. Use a new needle every time and tie off well. Use enough water that the cat doesn't start to crystallize, also not too much to make handling the syringe difficult. .05g for .1ml is a good ratio, I think. So .5 will fit into a 1cc syringe. So .3-.4 will be about 60-80 cents. It helps alot overall to heat the solution before you draw it into your syringe, and of course, use a cotton to filter it, but it should draw up fine without one. That's really all you need to know.
Stay safe and enjoy o7