Autothority Chip for 1.8T?

["W. Lemley" <wlemley@u.washington.edu>]

Does anyone have any experience with the Autothority chip for the 1.8L
Turbo?  Car & Driver just finished their long term test of a Passat 1.8T,
and they had installed the chip and tested both performance and on a dyno.
Power was up to 195hp, and 0-60 times down to the mid sixes (I don't have
the article here).  This sounds too good to be true for only $400.  My
questions are: How does it affect drivability (more turbo lag, decreased
throttle response, etc)? Does it void the powertrain warrantee?  Is it
something that could be installed and then uninstalled if warrantee
service was necessary?  And most importantly, how has it affected
performance on the slightly heavier Audi? (I am interested in possibly
installing one in an A4 Avant 1.8T).  Thanks in advance.