How important is ballscrew alignment?

I've installed a ballscrew for my X-axis on my 3/1 mill and it's a great
improvement!
I've just used it for testing and one small profiling run so far, and it
seems good.. No backlash, deadly-fast speed (so much so I turned it down
because it scares me)

But now I am getting paranoid - it was very difficult to align the
mounting which sits on the Y-saddle with the ballnut, especially in
ensuring that the angle is 90 degrees exactly. It all moves and works
quite nicely, perhaps just a little stiffer than I had imagined it to
be, and this is what worries me. How fatal is it to have this every so
slightly out of alignment? Will my ballnut/screw fail in 100 hours? Or
is it OK to have it not absoloutely perfect? Remember this is a Chinese
drill/mill thing, so it's not exactly a precision instrument to start
with..... so I expect some play in the system. (I have angular contact
bearings, if that helps! :P)

I guess my question is, if this alignment is out, will it just result in
loss of efficiency or mechanical-tragedy?
Thanks!
Abby