I am a full time student, and am often gone for 8 hours and over. We have two poodles, one 7 lbs and the other 14 lbs. We have always crated them and they are completely housebroken. We got Daltrey, the smaller one, when he was 10 weeks old and Mojo when he was 5 months old. We have always left them for extended periods of time and never had any problems. Both dogs are completely housebroken, and were easily trained. They took to housebreaking very well, despite our absences.
When Daltrey was little, we had a bigger cage for him, so that if he had an accident, he could "get out of it". He would sometimes pee, but never poo in his crate. We moved him to a smaller crate once he hit six months, and we have never had a problem since.
Mojo had been at a puppy broker in a crate since he was 8 weeks when we purchased him at 5 months. He was already crate trained when we got him, and it only took us 2 weeks to completely housebreak him.
I have had no problems with being gone 8 hours and leaving them, but I do give them lots of attention when I get home, and Daltrey isn't crated at night. (Mojo is too hyper to leave out at night, but he doesn't mind his crate). They both get excercise and plenty of love, and probably are two of the most spoiled dogs in the world
If you do plan on getting a dog, (or two), definitely crate train. It makes everything so much easier. It helps immensely in both housebreaking AND seperation anxiety. Also, be sure that the breed you are getting is suitable for your lifestyle. You probably won't have tons of time to excercise the dog, so smaller dogs or dogs that don't need a lot of activity are probably most suitable. I did TONS of research before finally settling on poodles; I had always thought that little yappy dogs were sooo annoying, but the non-shed factor and the intelligence factor trumped the yappy (our two aren't yappy at all, so that is BIG PLUS!! We've trained them well
All-in-all, I would say go for it. As long as you do your homework and know what you're getting into, you should be fine.