Haven't seen or gotten my notice yet (late '05 model bought in August).
I'll just wait it out as I haven't had any flickering warning lights or odd
behavior problems....yet.

B~

I've been wondering about this too.  I've had two instances where my Prius
stalled momentarily, both at slow speed in residential areas and with no
warning lights.  The stalls lasted for 5 to 10 seconds, not long enough to
have much effect on my driving.   I'll press slightly on the accelerator to
maintain speed.  I sense what feels like a slightly rough idle and the car
fails to accelerate.  My speed drops slightly.  After 5 or 10 seconds the
sensation of rough idle goes away and the car accelerates to my target
speed.  I've got about 6500 miles on the car now so you can see this isn't a
common occurrence.

Yes, there has been a TSB (US Technical Service Bulletin) out for the
engine reprogramming for the occasionally reported stall incidents
(only fix if error reported to dealer), and I did expect that
eventually it would become a SSC (Special Service Campaign) which is
done pro-actively on vehicles so they don't experience any problems...
(There was a separate TSB that was replaced by SSC 40A, which then had
another TSB which was later replaced by SSC 40D, which then had another
TSB (EG047-04)...  It was only a matter of time before that became
another SSC...)

Anyhow, from the source:
Oct. 13 2005 Special Service Campaign:
http://toyota.jp/recall/campaign/051013.html

Here is the Babelfish translation (pre-mortar = Prius, NHW20 is the
model designation for the 2004-? Prius, Underhood carriage number =
VIN):

Service campaign of pre- mortar

Concerning the portion of the regular use car of the pre- mortar, from
2005 October 13th, service campaign of the below-mentioned contents (no
charge repair) we had decided to execute.

1. Phenomenon of vehicle
(1) There are times when the inhalation air quantity at the time of
engine starting decreases temporarily, as fail-safe function working
with engine rpm decrease, the warning light lights up, there are times
when it becomes motor travelling.
(2) There are times when the moisture comes in contact with the
terminal of the rotary sensor connector for the generator inside the
trance axle, as fail-safe function working with resistance change, the
warning light lights up, there are times when it becomes motor
travelling.

2. Contents of improvement
(1) The program of all vehicle and the engine control computer is
corrected.
(2) The grease for waterproofing is applied to all vehicle and the
particular connector)

3. Object vehicle
ZA-NHW20
DAA-NHW20
Pre- mortar
The object car it is included-Under carriage number, Production period,
Remark
NHW20-0001002 - NHW20-0130298, 2003 August 1st - 2004 October 13th,
(1)(2)
NHW20-0130301 - NHW20-0133242, 2004 September 23rd - 2004 October 12th,
(1)
NHW20-3000002 - NHW20-3013252, 2004 September 30th - 2004 November
16th, (1)
NHW20-7000000 - NHW20-7003412, 2004 October 6th - 2004 November 20th,
(1)

Note:1. Because also the vehicle which does not become the object is
included in the range of the under carriage number where the object car
is included, please inquire at the Toyota store of the vicinity
concerning details.
2. Production period of the object car differs from the time of
purchase.

Doing to apply annoyance, there is no excuse truly in everyone of
regular use, but making guide from the Toyota store, because it
receives, ahead of time, it comes to the pre- mortar handling store of
the vicinity and reservation receives store day and time, inspection
repair (no charge) to receive that it receives, it asks.

We apologize to everyone of regular use from thing and the heart which
very much applied annoyance.

http://pressroom.toyota.com/Releases/View?id=TYT2005101389230

Toyota Announces Voluntary Special Service Campaign on 2004 and Early
2005 Model Year Prius
10/13/2005 Torrance, CA
Toyota Motor Sales (TMS), U.S.A., Inc., will launch a Special Service
Campaign involving certain 2004 and early 2005 model year Prius sold in
the U.S.

On the involved vehicles, an issue with the program logic in the
Electronic Control Module (ECM) system may cause some or all of the
following warning lights to illuminate: Master, Hybrid System, Engine,
Vehicle Stability Control, and Brake. If this occurs, the vehicle will
enter a "fail-safe" mode which allows limited operation via the
electric motor. However, the electrically-powered brake and steering
operation will continue to function normally if this condition occurs.
The electric motor will also provide enough power to allow the driver
to pull the vehicle over and away from traffic. Once the vehicle is
stopped, the driver may be able to restart the gasoline engine in the
vehicle by pushing the start button.

Approximately 75,000 2004 and 2005 model year Prius vehicles may be
affected by this condition. Toyota is proactively conducting a campaign
in the interest of its customers.

Toyota will inform owners of the involved vehicles with a Special
Service Campaign notification letter sent via first class mail
beginning in late-October. Owners are requested to contact their local
Toyota dealer for diagnosis and repair upon receiving their
notification. Toyota will reprogram the ECM system at no charge to the
owners of the vehicle. Also, in certain vehicles a special dielectric
grease will be applied, at no charge, to a connector for the transaxle,
which may cause a similar condition.

Customers with questions or concerns should contact the Toyota Customer
Experience Center at 1-800-331-4331.