Seijin no hi

I wouldn't worry about that holiday jamming up public transportation. There might be a minor surge, but that's all.

Gardens in January? Pretty brown or white, depending on location.

Yeah, gardens are pretty bleak in the winter. Fall is the best season for gardens. (Skiing in Kyoto? I hope you mean Hyogo, as in Hachi Kita...Kyoto is no more than a basin.) Bloody cold for sightseeing, but popular spots won't be inundated with tourists so this is a good thing, if you can bear the cold. You can see quite a few sights in 3-4 days, given there won't be any crowds or throngs of tourists. Expect temples to be crowded in & around Seijin no hi, but this would make for some great photo opportunities as the young adults will be dressed up in kimonos and other finery.

Thanks,
We will ski in Hokkaido, not Kyoto. Just planning to sight see in Kyoto and should be equpped for the cold. Trying to work out which order we should do things in ie Kyoto first then Hokkaido or vice versa.( In terms of flights to and from Oz I think it is better to go skiing first but of course the skiing will probably be better later.) Any other suggestions for which temples might be best to see at that time of year or which indoor attractions you would favour or anywhere else you would go for a few days at that time of year? We like food (who doesn't?), classical music and natural beauty, but are not big on fashion or shopping. I would like to see Ryoan-ji, but have heard it can be impossibly crowded , which seems to sort of defeat the purpose..

I went to Ryan-ji around January 6 one year. It wasn't empty, but there wasn't a big crowd either (it will be busier at weekends). Maybe around a dozen people stood or sat on the terrace (engawa) contemplating the Zen garden. With a bit of frost and snow flurries, it made a pretty sight. Remember to wear THICK socks (or two!) when visiting temples, as you often have to take your shoes off and even with the supplied slippers on, you will feel the chill from the ice-cold wooden corridors. Most temples have no heating.
You will still see crowds at Kiyumizu-dera (big coach parties) and Kinkaku-ji, but other places are quiet - we were the only visitors at Ninna-ji, a World Heritage site.

The temples in Kyoto will be almost empty at that time. Most Japanese think its too cold for sightseeing. And they are probably right...wrap up warm. If it snows it'll be very scenic, if not then the gardens will be unattractive. Kiyomizudera and Kinkakuji are the most famous/popular sights. There are some nice museums too if the weather is bad.
For 'seijin no hi' in town you might see lots of young ladies dressed up in gorgeous kimono, very photographic.
Most people stay home for this holiday or go skiing. The slopes will be a little more crowded than usual but not overly so