Sorry for late reply only just read your post and you may already have committed to KAI.
June 2008 I visited KAI, AJALT and Naganuma after an exhaustive web/forum trawl and some emails.
KAI receptionist was friendly but a bit pushy re trying to get me to sign-up on the spot, their level check was pretty comprehensive and instant feedback from a fierce looking but sincere sensei there. Apparently the local Korean restaurants are ok for inexpensive Japanese Korean style food (going on Korean friends' advice). Also KAI takes credit cards which is no small thing in Japan and much more convenient. Rates well on forums by all accounts. They offered to let me watch a class but between the lines I was getting a strong sense of obligation to sign-up if I did that.
AJALT was more tailored and personal in their response and their level check more conversational but still structured and systematic. They let me watch a class the day I visited, two students in class getting 'man to man' teaching (hence hourly rate is more than the boot camp schools). Problem was they only run classes when three or more students sign up and they couldn't confirm the next class would be running. Also, there's only a couple of classes a week and you'd better like the textbooks if beginner-intermediate level (the Japanese for Busy People series gets mixed reviews, but there is a new edition out recently).
Naganuma reception, true to the school edict, only speak Japanese which can be challenging. The chap there showed me their learning material and an estimate of the ethnic make-up of classes. The Intermediate (JLPT2+) classes are 95%+ Chinese/Korean. Large classes (10-15 students usually) and the school has a factory like quality (it is big, it churns out graduates, and it is intense by reputation). I signed up for Naganuma and have been there since. Their methods are, on the whole, good (repetition of basic sentence patterns, grammar, kanji every day plus tape/reading practice) and the school has given me a good foundation for future study. Negatives are: large classes so few direct questions, competitive feel in classes so can be inhibitive/stressful, mixed level in class so some students are bored while others struggle, excessive number of tests/exams (pretty much every second day), and the 'direct method' they use for me didn't explain Grammar points very clearly. If you choose Naganuma be prepared for heaps of homework too. I've made a number of good friends there and had some fun social outings, plus some of the senseis are really involved and conscientious.
I'm in Tokyo for a while longer but will now focus on conversation practice and one-on-one plus immersion, my spoken Japanese is very stilted. One piece of advice I would have is not to get too absorbed in school/homework. The best way to improve your Japanese is by practice, especially workplace. You cannot 'buy' Japanese as a skill, and the best investment you can make is to get a part time job. Without exception all the gaikokujin fluent Japanese speakers I've met learned on the job, eg at a bar or flipping burgers. It may sound unbelievable (it did to me) but it is true. Unlike Jpod101, school book Japanese is somewhat lame, formal and lifeless.
Oh, one last thing- checkout your local Kuyaksho (ward office) as the free lessons are great (not what you'd expect if you're thinking 'too basic' either).
http://www.aikgroup.co.jp/j-school/engl ... /tokyo.htm