Not beating anyone up or anything, but I've run cat5 in several different houses now and despite the variety of construction, I've been able to get cable from point "A" to point "B" with only minor amounts of head scratching. It's often advantageous to follow pipe runs, heating runs (not inside the ductwork please), or other existing passages through the walls, ceilings, floors. Sometimes it's a bit tough, requires the aid of a contortionist friend, or just plain makes you sweat (low-headroom attics in the summer really suck).
In almost all cases, a wireless solution would have been much easier, but I just have so much more confidence in a wired connection. Once you get them in they rarely give you trouble.... unlike wireless. Oh, that's not to say all wireless is bad. Some wireless connections are extremely trouble free, but I think you're upping the odds of having some kind of nagging issue with wireless and those issues are rare with hard wire.
So my advice is to really have a look at this. It's really not all that hard.