Do you have one? If Yes, are they worth it or just a hassle to keep?!
depends on what youwill use them for. I had a very zen styled pad during colleeg and had a platform bed with a futon on it, but used it as a bed not as a sofa. The futon mattress was a 8 inch thick dense core with layers of cotton so it was very comfortable. both my brothers are also futon purists and have platform beds with futons for years.
Do not go for those cheap 4-6 inch thick futon mattresses especially if they are on one of those metal frames. they are niether comfortable to sleep on, nor to sit on. almost as bad a sofa beds.
If you are lookign for something that can work as a couch and guest bed, look at some of the Ikea stuff, their mattresses are high density foam and much more comfortable than a run of the mill futon. The prices will be the same as a good futon and frame.
Fraruds is right.. has to be eight inches valaa.. i slept on a sofa-cum-bed frame with an eight inch futon for over a couple of years.. I still think it's better than my $1500 mattress..
Friend of mine is looking for one for his living room.
His wife is still in Malaysia and he doesn't want to go get a sofa set without her being there. Futon would be nice, cos if it didn't work out, (yani bagum kay na'ak kay neechay na aya) he can move it to study, which is also his guest room.
It's great for extra-curricular activities too
futons are good but sometimes it can be a hassle folding and unfolding it if you're using it as both a bed and a sofa on a regular basis. They are pretty comfortable to sleep on though if you buy a good quality one.
Fraudz somehow I new you’d be big on futons 
Ahmadjee be sure to pick up a bonzai tree while your shopping for zen. PA you keep your money in your mattress right.
Thap jahil, bonsai, not bonzai, u are mixing bonsai and banzai :D
btw be careful what bonsai u get,some issue with bonsais are mold, and insects. thought i would ge u started on that for your UK pad.
I dont have a futon which is in normal use anymore, just a mattress for guests when the numbers exceed the bedrooms :D