Yes, I vote for spaying as well!
Maci will be spayed at 6mos mainly because we want to, but also because we have to. The breeder whom we got Maci from had us sign a contract not to breed the puppy. I think any reputable breeder would ask this of their customers.
Plus, like everyone has already said...getting your furbaby spayed will eliminate having to deal with the whole "heat" thing
and many health issues!