Well, I'm not actually applying to the JSIS graduate program, but I am a current undergraduate in the general Asian Studies track with JSIS. Generally I've found it to be a great experience, and the program is very well connected in the Seattle community. To be honest, I've been most impressed with the SE Asian professors in the department, but the China Studies professors are also excellent and the Chinese language program at UW is not too shabby either. Either way, although UW generally tends to be a little overlooked nationally, its programs in Asian Studies/affairs are generally thought to be some of the best in the nation.
I'd be happy to answer any specific questions you have about JSIS/UW/Seattle as well.