As a Realtor who is currently marketing a home on a corner lot, the lack of privacy in the rear yard is an objection often cited in the feedback from showings the home has had. The extent that this is a problem really depends on the property, though, as I have seen corner lots with fencing and/or plantings that addressed this issue.
Being the first home does add to the traffic going past the home, particularly if it is the only way into or out of the neighborhood. In a small neighborhood this is not so much of an issue so, again, it depends on the home's location.
I think it's safe to say being the first home on a corner does somewhat diminish the appeal of any home and the property will always have to be priced accordingly in order to appeal to buyers.