We were in Tokyo for a first time visit in Dec 06 (from the 18th until 25th) the week we spent there wasn't even close to enough time to see/do everything we wanted to Weather was great, no rain, a little chilly, but nothing a decent coat won't resolve. We had little kids with us so had to do some amusement parks, which are best visited during the week rather than weekends by the way. You will have a great time!