Before transition, I was Bi, and I'd go back and forth on what I liked. Previously to transition, I was mostly with women and only one guy. I'd say that I was mostly attracted to women.
Now after transitioning, I'm with my girlfriend still and I've been with one guy. I've gone back and fourth on what I'm attracted too -- I'd be attracted to females for a while, and then males.
Having slept with both sexes before and after starting my transition (only on HRT now, I haven't had surgery yet), I'd have to say I can't totally enjoy sexual relations fully until I get surgery. I hope anyway.
Previously to transitioning, I was with a lot of people hoping that I'd feel complete. It didn't work. I liked foreplay, but for me, sex was boring and didn't do much for me. Mentally, it was awkward. I knew who I was inside, so using my birth appendage felt strange, unsatisfying, and numb.
After HRT, I find the appendage doesn't work that well anyway, and it's the same thing. It's unfortunate for my girlfriend, which has created months and months of strain on our relationship. I totally understand her point. Toys are not that interesting for her, and they don't replace the intimacy of having someone in you (and I can understand that and appreciate that). Although she's attracted to me, she's pretty much straight. So, there is a degree of difficulty in that aspect. I don't get much out of being sexual with her, but I still like to hold her or have her hold me. She's tried doing stuff to me, but she generally has tried to do the typical straight thing (suck my appendage, grab it, play with it, etc) -- stuff I found very awkward.
She has never been in a lesbian relationship before, so I can understand how difficult it can be to know what to do or how to work a lesbian relationship. I'm in the same boat, I've been with women before but the dynamic was that of a straight relationship.
And since I have been living full time for a year, I find it more and more awkward to use it to accommodate and make her happy and get the strain out of the relationship. It tears me apart, actually. But I can't go back and be someone I'm not.
As for men, there was one incident. Being held and treated like a girl was a really good feeling for me. I never felt it before (it's different than a gay-man relationship). I think it was the one incident that made me realize what I wanted and needed in a relationship. The actual sex part was okay, but still I felt like something was missing.
And then again comes the thought: I'm not going to fully enjoy this until I'm complete.
So, now, I know what I want in a relationship. I think it's more of the dynamic of the relationship, rather than the gender. I don't know where I'll end up after surgery, I may end up sticking with a gender or maybe not. I think it would be important for me to explore my sexuality for a while after surgery.
My girlfriend, of course, is having trouble with all of this, and understandably so. And I would too, if I were in a relationship with someone going through such a huge growth and change. It's not easy for either party.