I have now made som more tests.
I have written a small program on my PC and i have setup Arduino to read the 16 potentiometers send their values to the PC program. I read the potentiometers and send the values every 10 ms and it doesen't seem to be a problem.
If the sensors you were thinking about using are the kind that send out a voltage (like my potentiometers do) i can't see why you shouldn't be able to read them just as fast.
One thing to note is that right now i don't do anything with the values on the Arduino, i just send them. In a real life situaton some processing would probably take place in the Arduino program, using a little more time.
MikMo
EDIT: I tried at serial speeds of both 9600, 19200 and 38400. The PC program seemd to be a little less responsive at 9600. 19200 and 38400 worked fine.