I have two littermates that just turned 6 months old. As for same sex littermates, i can't help out as I have a male and a female. Before we got our pups (and i mean a year to 6 months before) we started researching like crazy and saving up our money. We knew that the pups would cost a lot, we knew that the vet bills, toys, crates, etc. would cost a lot and as we saved we bought little items here and there to space out the cost.
When it came time to get the pups we already had everything we needed for them to be happy and healthy (crates, toys, food bowls, food, a good vet, etc). We also had enough money to purchase both pups and pay for their shots and the other surprises that came our way. Two weeks ago we had them spayed and neutered and had enough money to cover that. I think if you plan wisely, save your money, and devote the necessary time littermates can be wonderful and be very rewarding. But like i mentioned earlier, i know my situation is unique and that many cannot afford, nor devote the time and energy to 2 puppies. (We still don't have cable tv in our house- just as an example of how devoted we are).
I have to say that my experience is as unique as every families experience is. My experience is unique in the fact that our pups have been such a blessing and not at all an inconvenience. We got them at 9 weeks old and I immediately took a 5 day stay at home. We moved our matress and their crates to the dining room and slept there for 3 months so that the pups had easy access to the door to go outside. For the first month we only allowed them in the kitchen and the dining room where messes could be easily cleaned up and where they could see the door that led outside. We never left them unsupervised (unless they were crated) and had very few housetraining accidents. I must say that to make this all work we did devote much of our time to our pups. After i took off 5 days, my fiance would come home from work 3 times during the day (about every 2 hours) and let them out to play and pee. Now, i'm currently off of work for the next 2 months and i still devote much of my time to my pups.
I definitely would not reccommend littermates to anyone who doesn't have the time or money to devote. But as for the comment that the pups will bond with each other and not you i have to disagree from my experience. Our dogs do love each other very much and they do play with each other a lot which allows me time to read a book outside while keeping an eye on them while they play. But they do love us very very much. THey always try to curl up with us. Whenever my fiance or i sit on the floor one or both try to lay on us... they always want to curl up with us in bed and no matter what room in the house i am and no matter how hard they are playing they always manage to play in whatever room I am in.
I think it all depends on the situation, the puppies themselves, and the time you have to commit. Best of luck