All floating point textures seem to get their coordinates inverted. I don't know if this is a generic mesa bug or something specific to r600 as swrast doesn't support float textures yet. Works fine with fglrx though. I've confirmed the issue by using the exact same program and just switching between a GL_RGBA16F_ARB and a GL_RGBA texture. The first gets both the s and t coordinate inverted and the second works fine.
The swizzles may be wrong for some texture formats. See r600GetTexFormat() in r600_texstate.c.
As Alex guessed, it was a swizzling problem, not a coordinate one (the texture I was using made the it more or less impossible to tell the difference). Patch has been sent to Alex, and is also available here for a while: http://pastebin.com/m72ead66
pushed: c9befda13a000f7ad2221e957615c909bff279f8
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