I have run any number of wires throughout my house which is why I made the recommendation I did. It should be added that while HDMI is great, you will find more than a few horror stories here, so you may want to go ahead and run two HDMI cables, and component, and composite, maybe CAT-5 as well for later networking of your TV, or to put a Wii transmitter, or IR repeater under the display.
There are so many reasons to open up the wall, and just a few (big) reasons not to.
The biggest, and most obvious reason is that there is likely no real way to get a 'perfect' match to the existing paint job, so you really will have to repaint the entire room.
But, this is the time to do it. It's your new home, and a fresh coat of paint in the family room is a killer thing to do. Plus, the other things you could do at this time would make it a real attraction for years to come.
My two most similar incidents in my new home...
1. Running power up to lighting in my study - There was a couple of 2x4 fire stops in the way of my cabling run along with a pipe for the bathroom. I just cut a couple of holes, drilled through, ran the wires I wanted and then patched them up. To do a good job, I put on several coats of spackle and sanded several times.
2. Kids playroom, installing 32" LCD. I wanted it centered on an outside wall but hadn't run conduit to that location. So, I cut a hole up high on the wall where cables were to drop down and drilled upward into the attic. Found the spot to drill into, and ran cables from the attic down - into an insulated outside wall, and then fished them down to where the 32" LCD currently sits. Patching, once again, was just a couple of days of spackling and sanding with a fair bit of waiting for spackle to dry.
The painting in these locations was easy enough because it was a new home and we had the correct shade of paint on hand.
Fishing wires can be done for many things, but quite often, it just isn't a practical solution, and you end up fighting the limitations of what you can do, instead of doing what you truly want to do.
If you're just moving in, and it's your house - do it all NOW! Make the most of it and enjoy some recessed/zone lighting, bury the 7.1 channels of audio in the wall. Move the rack from next to the fireplace, to next to the couch so it doesn't mess with the line of sight in the room. There are so many options you have available to you it's really a very cool open door.
Don't let that drywall hold you back.
From what I've seen with Best Buy wiring, it typically isn't very pretty and I've only encountered straight down drops of wires from them within the same stud cavity. They could probably do an in-wall of this level, but it likely wouldn't fall under a 'basic' installation cost which they may advertise. Yours would be a retrofit, no access level installation - which typically increases cost significantly.
