HLSL documentation says:

[in] An optional texture coordinate offset, which can be used for any texture-object types. The offset is applied to the location before sampling. Use an offset only at an integer miplevel; otherwise, you may get results that do not translate well to hardware. The argument type is dependent on the texture-object type. For more info, see "Applying Integer Offsets".

I'm worried about "do not translate well to hardware" part. #1024 adds a whole ton of offset-enabled texture sampling functions, generally with non-integer mipmap levels.