The patent covenant only applies to software that you develop at home and keep for yourself; the promises don't extend to others when you distribute. You cannot pass the rights to your downstream recipients, even to the maintainers of larger projects on which your contribution is built.
Further, to qualify for the pledge, a developer must remain unpaid for her work. Experience has shown that many FOSS developers eventually expand their work into for-profit consulting. Others are hired by companies that allow or encourage Free Software development on company time. In either situation, Microsoft's patent pledge is voided for that developer.
Even if the patent pledge were to have some use aside from these problems, our community simply could not rely on it, since Microsoft has explicitly reserved the right to change its terms at any time in the future. A developer relying on the pledge could wake up any day to find it revoked. She'd have to cease development on her non-commercial and (mostly) non-distributable modifications that were previously subject to the covenant.
And then he gets mad:
Don't be confused by the illusion of a truce; developers are no safer from Microsoft patents now than they were before. Instead, Microsoft has used this patent pledge to indicate that, in their view, the only good Free Software developer is an isolated, uncompensated, unimportant Free Software developer.
I am certain Microsoft will deny all this. But of what value is that denial? Open source programmers must now match the track record of the former executive director of the Free Software Foundation against the track record of Microsoft, in terms of support for open source programmers. No contest.