I'm with an ISTP now and I can tell you some of my experience. First, I was not initially drawn to him and I don't think he really was me, either. In an attempt to hook my friend up with this roomate, we all agreed to hang out group-style but everyone ditched except us. So we decided to carry on. Being around him was very, very easy from the get-go. It's hard to explain but we could just be in a space together very comfortably. I did not feel the need to talk and engage as much as I usually do, and he seemed to open up alot more than normal. We closed a psychological gap faster than I have with any other type. Part of this is because he is hands down, the least judgemental, critical person I've ever come across (e9) and very emotionally raw.. like zero head-games, zero ego-trips, wouldn't know how to be emotionally manipulative if he tried. So while he did not open up his feelers much, and he was kinda incapeabe of introspection.. whatever he did say or do was as authentic as it gets, and this made me feel very safe.
The sex was HOT from the beginning. Probably best first-sex I've ever had with anyone. No hold-back at all, he was even more ready to do crazy, kinky, unspeakable acts and positions than I was! And there was no fear in any of it (how does he feel, what if he doesn't like this, etc) because the bugger likes just about everything I could conjur up, lol. After we had sex a few times.. I just flat out told him that I only sexually engage with 1 person at a time, and asked him where he stood on this. He told me he was the same and didn't really see a point in dating others either, he was happy right now. Me too!
Any kind of fweelings and theorizing took a back-seat to the amount of fun experiences we had. I have never, ever met anyone so willing to go along with my crazy whims and shenanigans. If I thought it, we did it.. almost instantly. SP's are bad-ass I tell you. It's 2am on a tuesday night, lets go ice-blocking with a bottle of wine at the park.. let's hike up to the nudist natural springs, let's drive to a resort and rent a room, smoke weed and jump on the bed, get up the next morning and go sushi-hopping, we'll come back, have a few drinks and go swimming in the pool. No fear, no hesitation, no planning.. just go. Deal with what comes up along the way. FUn FUn Fun. I also never feared him cheating or lying or suddenly leaving.. because I saw the gleam in his eye when I was around. I could read it on him like neon-sign.. the way his face lit up, the way he always looked to me or for me at parties.. even if some silly-ho was in his face shaking her boobies.. he'd look for me.. and I'd be across the room grinning my ass off. He actually showed more jealousy (initially) than I ever did.