Perhaps the Most Truthful: on Microsoft marketing:
There wont be anything we wont say to people to try and convince
them that our way is the way to go.

Not on his mind while developing Win9X..circa 1981…
640K ought to be enough for anybody.

On the solid code base of Win9X… thanks WPW!
If you cant make it good, at least make it look good.

from OS/2 Programmers Guide (forward by Bill Gates):
I believe OS/2 is destined to be the most important operating system,
and possibly program, of all time. As the successor to DOS, which has
over 10,000,000 systems in use, it creates incredible opportunities for
everyone involved with PCs.

Bill Gates, Free Market and the LA Times Thanks GC!
There are people who dont like capitalism, and people who dont like
PCs. But theres no-one who likes the PC who doesnt like Microsoft

From the back of an old Digitalk Smalltalk/V PM manual, 1990:
This is the right way to develop applications for OS/2 PM. OS/2 PM
is a tremendously rich environment, which makes it inherently complex.
Smalltalk/V PM removes that complexity and lets you concentrate on
writing great programs. Smalltalk/V PM is the kind of tool that will
make OS/2 the successor to MS/DOS.

from OS/2 Notebook, Microsoft Press, (c) 1990–an excerpt from an
interview with Bill Gates and Jim Cannavino, p. 614:
Developer: Does the announcement [of the OS/2 joint development agreement
between IBM and Microsoft] mean that Microsoft is curtailing any plans
for future development of Windows?
Gates: Microsoft has not changed any of its plans for Windows. It is
obvious that we will not include things like threads and preemptive
multitasking in Windows. By the time we added that, you would have OS/2.

Theres a reason they threw it away…
from Programmers at Work by Microsoft Press, interview with Bill
(found on comp.os.os2.advocacy),
Interviewer: Is studying computer science the best way to prepare to be
a programmer?

Gates: No, the best way to prepare is to write programs, and to study
great programs that other people have written. In my case, I went to the
garbage cans at the Computer Science Center and I fished out listings of
their operating system.

Only the finest Microsoft marketing! (submitted by BarryB):
If you dont know what you need Windows NT for, you dont need it.

On the Box of Windows 2.11 for 286 (submitted by GLDM)
New interface closely resembles Presentation Manager, preparing you for
the wonders of OS/2!

On code stability, from Focus Magazine (submitted by Benedikt Heinen
Microsoft programs are generally bug-free. If you visit the Microsoft
hotline, youll literally have to wait weeks if not months until someone
calls in with a bug in one of our programs. 99.99% of calls turn out to
be user mistakes.
[…]
I know not a single less irrelevant reason for an update than bugfixes.
The reasons for updates are to present more new features.

Unconfirmed quotes:

Microsofts GUI innovations… 1983 (thanks E.R.)
Imagine the disincentive to software development if after months of work
another company could come along and copy your work and market it under
its own name…without legal restraints to such copying, companies like
Apple could not afford to advance the state of the art.

Even more 1984 predictions (thanks Scott Renyen)
The next generation of interesting software will be made on a Macintosh,
not an IBM PC.