Depends if you want your head gasket warranty to be honored.

Since they took the time and expense to issue a recall on the issue,
and print new manual pages including instructions to use it, my guess
is "yes."

Good news is that's it's not expensive stuff.

--
Todd H.
2001 Legacy Outback Wagon, 2.5L H-4
Chicago, Illinois USA

There is a problem with coolant leaks in some Subys. Seems like a small
investment for peace of mind. Check with a dealer for the need in your
particular application.
Sparky

Yes, it is needed if your car fits the recall. All signs are that it is Holts Radweld:

Subaru magic conditioner:
http://www.scoobymods.com/forums/attachment.php?s=a75d1dba0f4a4ac808a7695c6930b2
b8&attachmentid=2230&d=1077312572
(notice "Holts" on the bottle).

Radweld:
http://images.hemalhemsat.com/_upload/200611/890471001142339048873872_0_0.jpg

Is this needed for ALL 2.5 L engines, including turbo and 2007 models?

As near as I can figure it the magic conditioner is little more than a 'Rad
Stop-Leak' deal which is being used to ease those engines past their
warranty period before they inevitably digest their head gaskets.

As one who has had the head gaskets done twice under warranty,  the second
time resulting in the replacement of the entire short block,  and once after
that at a non-Suby garage I can attest to the fact that there is indeed a
problem with the 2.5 head gaskets,  and that Subaru dealers have been less
than forthcoming about it.

Once I had the job done by my own garage using aftermarket gaskets rather
than the Suby ones,  the problem stopped.    My mechanic tells me that every
Suby on which he used o.e.m. gaskets developed leaks again,  and every one
on which he used aftermarket gaskets has not.

Neither of the two Subaru dealerships which did the job on our ' 99 Forester
did a proper job at it.  Both claimed to have had the heads magnafluxed and
skimmed to ensure flatness,  but when measured after that the heads were
still stock thickness,  clearly indicating that service managers at both
dealerships lied through their dentures.

The heads and block deck were scratched in a manner to suggest that someone
removed the residue from previous gaskets using a piece of 80 grit sandpaper
artistically wrapped around an index finger.

If I were in the position of the original poster I would use the conditioner
as prescribed as a term for warranty validity,  and as I neared the cut-off
date for warranty work I would have the engine leak-down tested on a regular
basis in order to try to spot gasket failure before the buggers can legally
deny you the job.

I love the Suby,  but their service in this part of Canada is the pits,  to
be kind.   The scarcity of dealerships here also poses a logistic problem
for warranty service.   Trips of 100 miles each way to the nearest dealer do
not improve ones' attitude once he gets to where he is about to be lied to.

KH