Elektron Musical Instruments

...and i have a couple of questions for those of you who already have
one! i'm thinking about replacing a 909 with a md for live use.

can you edit patterns while it's playing?
i more or less improv the drum parts so i'd like to leave it on a
single pattern and edit the notes in that pattern, like i do with the
909 now. i usually step edit the notes in and out, so the fact that
the pads are apparantly not well-suited to tapping in things live
doesn't bother me.

related to that: how do the pads feel? clicky? smushy? nice technical
terms there, eh? :)
any other drum machine who's pads you'd compare it to? they look like
they're similar to the pads on an 808 or possibly an electribe, but
looks are frequently decieveing.

last question: how many rack spaces does it take up when racked?
from the dimensions on the website it measures out to 4U, but with the
audio ins/outs on the top i'd have to assume you need to leave at
least 1U empty space above it, right?

thanks a bunch in advance for any advice any of you can offer!!
john.