It is an limitation, and there are no hacks for it, but that doesn't mean there can't be. The 6700 has the same problem, but emulamer came out with a hack for it (http://www.emulamer.com/6700kbfix.html). I wanted to write a similar hack a while back, hopefully being kicked off by getting the source code to the 6700 hack (which never happened), but I fell off the face of the earth and just started reading the forums again. I don't know that I particularly want to do this from scratch, but we'll see.

It is incorrect to say that it is a hardware limitation -- it is not, as can be clearly seen from the fact that the Fn and Shift keys support multi-press. If you hold down a random letter key, say A, in a note until it starts repeating, and then press, say, B while still holding A down, A will stop repeating, but B won't show up. However, holding down Shift and then hitting B gives you a capital B, just like a single press of Shift and B does. So either the keyboard controller is either dealing with different scan codes differently -- remarkably unlikely -- or we're dealing with a firmware/driver limitation that we just don't know where to look for yet.

As an alternative, there are bluetooth controllers you can use with the phone which allow multiple button presses; however, there seems to be a bit of delay when using those, so that twitch games can't really be played. I'm not sure if the delay is just a necessary consequence of its being bluetooth or if there are other reasons. I haven't had any luck finding a keyboard that'll plug in directly that works either; I tried the i700 keyboard, but didn't have any luck getting it to work.