I have a few theories about lockouts:
1) Unless they are remotely controlled, you will never (or very rarely use them). Unfortunately, remote lockouts add cables and clutter to the cockpit.
2) If the fork or shock have a stable peddaling platform (such as the Fox ProPedal), the lockout becomes much less critical.
3) If the bike rear triangle is designed well and the stable pedaling platform is effective, lockouts are almost useless - unless you are a racer and need to put a lot of emphasis in strong starts and uphill pedaling efficiency.
So what does all that mean? For me (I have a Trek Fuel 98) it means that I never use the lockouts, front or back. I simply find that the bike is remarkably efficient. Once in a while the shock lockout (mine is not remotely controlled making it even more useless) gets flipped to the locked position (by a branch or something) and I hardly notice that it is locked. And it is usually rough terrain that makes me notice that the shock is locked. Pedaling alone does not (unless I jum out of the saddle). Of course, I tend to pedal in the saddle and I naturally go for a rotary motion so a locked shock gives me minimal advantage.