I'm generally happy with taking OL high in the draft. It is one of the most sure postition grouping in the "non-bust" category IMHO. However, like Kip said, guard is not really a position of need. We need tackles more than guards, I think. And there are other priorities, though I'm not so sure we can write off Irvin as Clem's eventual replacement yet. It's only been 10 games.
If he was BPA is a big if IMO. Part of the whole "BPA" evaluation has to include his fit in the team and at least hinting at team needs. BPA gets really tricky when you start to compare "skill" positions (the sexy picks) to the "non-skill" positions (the boring ones). There are those who would never consider an OL the BPA, except maybe in cases like Walter Jones.
But like I said, if they went 1st Rd OL every draft, I probably wouldn't mind.