Very very important when looking for this restaurant: both Apple Maps and Happy Cow list it in a totally wrong place. The full address is 京都府京都市中京区衣柵通御池上ル下妙覚寺199 イチイビル1F. Google Maps is your best bet for finding it. Copy and paste the full address that I just wrote into Google Maps, and it will put a marker on the right spot. The building will say "ICHII BLDG" on the side in roman letters. The street name is Koromonotana Dori, just a block north of Oike Dori. There is an 'area map' on Koromonotana Dori and the corner of Oike Dori, on the same block (and the same side as the restaurant). If you find the map, start walking north and the restaurant will be on your right hand side.
I went to Obanzai with some US friends (all vegeterian). The restaurant is still very much open, at least as of December 2013. Its names is only written in hiragana, so if you don't know how to read Japanese you'll want to write down the name and do a little pattern matching (おばんざい).
The vegeterian food here is delicious! They have fried wheat gluten, many types of tofu (Kyoto is famous for its tofu, and Obanzai is no exception), and all the things you would expect to come with a kaiseki meal: pickled vegetables, seaweed, miso soup, rice. They also have yummy cookies and soy milk-matcha tea lattes.
The restaurant operators speak enough English to get by if your Japanese is not good. They'll tell you what has fish if you say you're vegetarian. I have been there twice and there has only ever been one fish dish out: pickled herring, so it is quite obvious and easy to avoid.
Buffet dinner is 2100 Yen/person. Service is pretty limited: they'll tell you to sit anywhere you like when you come in, and leave on your own to chow down. If you want extra drinks (tea and water are free) or special food, go to the counter to order them.
Updated from previous review on Monday December 02, 2013Pros: Great food, Lots of food (all you can eat), Friendly and generous owners
Cons: Tricky for those that don't know Japanes, A bit pricey