The senshusei course is great training. It develops the spirit and teaches solid fundamentals. All too often you find aikido with very poor understanding of fundamentals. Schools open up with someone whose maybe trained 2-3 times a week for 10 or so years, then open up their school and teach the same way. At the senshusei course, you will be spending months breaking down the fundamentals of each technique. Eleven months is quick to promote to shodan, but you will have a solid fundamental understanding of the basics. Now, a yoshinkan student whose been training for six years to shodan, has done extensive, ind-depth, courses is going to be overall more well-rounded...as they've just had more time on the mat. But you will progress more in the senshusei course than you would in years training at a regular, part-time dojo.
Yoshinkan is often commented on, and judged by, people from the outside. As far as 'gritty,' I don't really know how to put that in context. As far as 'original aikido of Ueshiba," Yoshinkan aikido is much closer to what Ueshiba was originally doing with his training. Yoshin means 'cultivating the spirit,' which is the primary focus of Yoshinkan training. This is why you see Yoshinkan classes as having very high levels of energy - really putting themselves out there, and pushing themselves past their limits in order to facilitate "spiritual" growth.
Let me clarify some of K-mans comments on Yoshinkan movements:
The video displayed is kihon dosa, which is training of body movements. This is first done tandoku, by yourself, then sotai dosa, with a partner adding some resistance. From there they add kanren waza, practical application. Its a particular set required for shodan testing candidates. The principle being to learn to control your own body before attempting to manipulate someone else's. The movements train a student to keep weight underside, maintain one point, extend ki, etc. In a crawl, walk, run approach the student learns to control his body movements, control his body movements with resistance, execute technique when uke has already grabbed you, then execute technique when they are striking you. Traits of Yoshinkan aikido are efficient use of movement and energy. Compromising uke into poor position while nage maintains solid posture.