My speed has remained constant. Perhaps increased slightly actually in some areas. I've gained a lot of strength in my lats from all the chins, which seems to have improved a lot of my strikes.
My footwork and coordination has improved a lot since starting HST. My reflexes have always been very sharp, but they seem to be better lately too. All in all, it seems like HST has only been a benefit. I think as long as I don't go overboard and get as big as Jay Cutler (yeah right) I should be fine.
I've been considering crossing over into JKD for quite some time, actually. Unfortunately, everyone around here that "teaches" it are pretty much clueless.
I'm a big fan of Bruce Lee, my teacher is as well, having been taught by the son of Bruce Lee's Wing Chun instructor... I'll probably just buy a few of Bruce's books on JKD and see if I can apply the knowledge myself. A lot of the basics of JKD are quite similar to Wing Chun - no surprise considering Bruce's training - so it shouldn't be too difficult to get myself started on it without any official training in it.
They have a class at my school for full contact sparring that doesn't teach one strict type of Kung Fu but actually incorporates techniques from several different martial arts to try to give you more "real world" experience. I'm considering taking up that class. Unfortunately due to my schedule, I'd have to drop Wing Chun in exchange... so it's a bit of a dilemma.
I know what you mean about finding sparring partners. I can spar with people when I'm at class, but outside of class, no one I know wants to spar with me. My wife too Wing Chun with me for a year or so before she quit going, so she knows somewhat what she is doing, but she's scared to spar with me...
However, I've been training my younger brother for some time now, off and on, in the hopes of creating a sparring partner. Heheh. He's getting pretty good too. There are a couple kids at work that want me to teach them too, so who knows. Maybe I'll have a sparring partner soon enough.
Really, I just want someone to Chi Sau with, so I can practice outside of class more.