Re: bokken vs bokken?
Several aikido styles, including but not limited to Saotome sensei's Aikido Schools of Ueshiba (ASU) include paired weapons kata (bokken and jo) as integral parts of their teaching syllabus from day one. In fact, Saotome sensei made a big point of stressing the importance of weapons work to the folks who attended ASU Winter Camp in DC this year. The official ASU Student Handbook has testing requirements for these kata beginning with the test for shodan.
As I understand it (I hope someone like Ledyard sensei will clarify anything I get wrong), weapons are a great way to magnify what students are doing so one can more readily see errors in distance, timing, footwork and center-to-center geometry more clearly. They also help to encourage the development of center, smoothness and the requisite martial spirit.