Catered more towards 20-40 year olds, Oktoberfest is a great place if you enjoy drinking and being merry, with a great atmosphere built around a theme park, beer tents and all round merriness.
Oktoberfest runs every year for at least 16 days starting in September. It ends on the first Sunday of October or on October 3rd, whichever is later. We concentrate our tour on the last weekend, which is busy and fun, but not as busy and packed as opening weekend, enabling us to get better areas.
So, you will be drinking steins, so these are 1 litre. So while they cost upwards of £10 a stein, it's not too expensive, and you definitely won't be going onto doubles and mixers in the tents. Your first beer though is on US!
In our opinion not, the problem with the tents, similar to at Running With the Bulls and similar festivals, is that you need to get a bus out of the city which can take a long time. Also, does anything beat a nice bed to sleep in when drunk? That's why our tours work with local hostels.