i did a contiki tour in july this year - "european vista" - for 21 days in france, italy, austria, switzerland, germany and the netherlands. contiki has a few types of tours, camping, hotels or hostels. it is expensive when you add on everything like lunches, extra sightseeing, beer money.. but it is soooooo worth it!!!
For the party aspect, it is what you make it. If you want to go drinking every night, there will always be people to go with. But if you don't want to, nobody forces you. eventually you get tired so you need to take a few nights off. i think i went out late for about half the time, for just one or two for a few nights and didn't go out about 5 times. its up to your stamina, i guess.
yes, you do heaps of sightseeing. by the end i thought if i saw another church i would be sick! but mostly it is just the highlights of whereever you are. but you also spend a lot of time travelling. you just have to pack it in to get the most out of where you are. like we only had a night and morning in florence, by far my favourite city. i went back there after contiki by myself and saw so much more than what contiki could have shown.
you can tell there is a well worn contiki path - they always go to the same shops where the same bored person dressed in national costume will tell you how they make something from that country. then you will be pushed into a gift shop where you can buy it for double everywhere else.
but definately go on optional excursion and dinners..... good times!
there were 46 in my group. if you go with another company they probably won't have as many. the gender mix was even, i suppose it depends on who books when. i made lots of friends from contiki, but i only keep in touch with 3 now.
other companies that do similar things in europe are budget expeditions, topdeck, intrepid and haggis/shamrocker for uk/ireland only.
hope this helps.