In Project Server 2007 the Project Server Interface (PSI) was designed to expose as much to developers as possible. But of course along the way certain compromises have had to be made (as happens if you ever want to ship a product). I want to point out one such spot I just ran across in case this will impact you in your development plans.
Every task has a notes section associated with it. The note section allows you to richly format the text in it (i.e. multiple fonts, settings, etc). These are converted to binary and saved in the RTF format in the Project plan. In the case of Project Server they are saved in the TASK_RTF_NOTES column as the SQL type of image. The PSI does not handle the writing back of the image data type. This makes TASK_RTF_NOTES a read-only field. There is information about this in the documentation for the CreateProjectFormTemplate method in the Project Server SDK. The SDK team is going to add this information in a more appropriate spot also.