I'd have to pick the Alien. Not for rage or raising your own army, I just liked being incredibly fast and being able to take out just about anything with just melee (Rage was more annoying than helpful to me, since I could never seem to hit anything while using it). She can also use a decent amount of equipment, though less than in 1.2
The Human is a nice, all-around sort of character (which is probably the intention), and pretty non-descript. His speed feels slow, though, and it doesn't help that there's nothing special about him to make the game interesting.
The Android seemed a bit underbalanced, though. Despite that, I still kinda like it, since I can usually get obscenely huge batteries, then just use a Fuel Cell once in a great while. The enhanced speed helps plenty, and I use primarily a pebble shotgun early on, or a VC pistol if I can get one. Since I just blitz through most areas with the Android, ignoring most items not detected by the scanner (aside from pebbles and bullets), I never even have to worry about energy much; I can usually even out from electric plants, and only carry a few batteries for emergencies.
The psionic is fairly frustrating, though. The low food requirement is nice, but aside from that it feels like a handicapped character. Almost *nothing* is usable, not even brown aliens (which kinda worried me when I figured that out). Energy can run out frustratingly quickly if you keep getting attacked (especially in the Hive), and it also takes forever to regain. Not so bad normally, when Electric Plants are decently plentiful, but in dreamscapes I often have to carefully ration my energy. Although, in the end, the Psionic becomes pretty powerful with the Lifeforce token, and then nearly omnipotent with the Void token (Store up masses of Life essences, then convert it to energy whenever needed), but searching entire maps for dreamscapes is gets tiring pretty quick.
You actually summed up the races very accurately and at least depicted to some degree what I was going for. When I designed the Psionic and redesigned the rest, save the human which wasn't changed drastically I had certain goals in mind. You at least outlined what they were with your summaries.
The human has always served as a good middle ground and even with the various advantages other races have it's the fact that it is the middle ground that makes it more accessible. It also can get one of, if not the most powerful ally to start with, which is exclusive to the human. I'd still say the human is one area I plan to improve upon. In the end you can view the human as the template all the other races were built off of which makes playing the human a good step in getting better with the other races.
The android's gimp on health came at the realization that people were finding the android very easy and I personally ignored my health because it had so much and was so very easy to increase. The fact that you have to really manage an Androids health makes sure you're careful. In nearly every other area the Android has a good advantage over others, so the healing factor was the best way I found to gimp it.
The Psionic was planned almost exactly as you described it. It was meant as a good challenge which obviously can translate to frustration for some as any challenge usually does. Over time and with practice players will however find that the Psionic can become incredibly powerful which is the reward for sticking with it when you can obviously just go with an easier race. I am actually glad you can't go into the Hive, blow your energy. The Psionic was planned as a mage type race and that's why it scales up in power and plays the way it does.
The alien wasn't covered by you but I'll explain that one as well. One of my main goals was I wanted a type of experience bar, but I didn't want it being a strict experience bar. You've got some form of tangible progression and to boot the alien turns into the powerhouse it always envisioned itself as. Things that were part of the evolution were either to compensate for not being able to use something, like the night vision and creature detection or because they otherwise seemed logical like laying eggs.
My final goal if any will be to hopefully get each race to a point where the enjoyment of each is both unique and enjoyable without being too easy or difficult. I definately appreciate this thread as it helps me see what areas need tweaking and what worked and can possibly be improved on further. I definately understand that not everyone is going to agree with the changes, which is why I at least hope every person can find one race that they enjoy out of the four and possibly learn to enjoy the others later.