some dogs are ok left alll day other arn't massivly depends on age breed and the personality of that particular dog.
i can leave mine all day no bother as long as there is a massive walk beforehand but only ever do it on a needs must basis. but usally comes to work with me and just chills out in the back of the pickup
I have a Colie Cross and a Yorkshire Terrier at the moment, always had dogs though.
If you have a big house, we found Great Danes were a good dog, not much excersise needed, doesn't eat too much (given the size!), but they don't live too long though, and will easily take up a 3 seater sofa!
Also had a Chihuahua crossed with a Pug (Ugly little fcker!) which was ok to keep, easy to walk and feed etc, liked attention...
Had another collie cross, most loyal dog i've ever known!
Overall it depends what you want, and how you train it. All the dogs i've had have been fine with being left on there own for hours on end on the odd day, and our current 2 regularly have 1 day a week where we are out for 8-12 hours and can't take them. The Collie is about 11 (Rescue dog) and the Yorkie's around 18months (Again, rescued!).
If you do get one, and it is left and does something in the house though, don't tell it off when you get home, dogs won't put 2 and 2 together and realise that what it did hours earlier was wrong...
Train it right, and it'll be your best friend! Also, don't read into the personallities and perseptions of different beeds too far! I have a friends with a Rottweiller, built like a brick sh!thouse but soft as you like! Same with a mate with a Staffie. Although certain breeds are bred for a purpose, bringing them up right can easily change them into an ideal pet. Leave it constantly, give it no attention and don't feed it properly and it'll be pretty angry...