Yeah, this is a problem for me.
As someone who practices martial arts as well (mainly Wing Tsun and Latosa Escrima) I completely agree with this.
Real-world martial arts examples are pretty useless since 4e isn't about simulating real-world martial arts.
It's not a martial arts trip.
It's basically "I knock them over." In 3e, I imagine a trip attempt as basically a strike at the legs, or a push or twist that should knock someone off-balance enough to fall over. It's a low sweep with your sword, it's an off-centered shove that sends you spinning, it's you getting in their face and pushing them over your foot.
And it requires no special training to really grok that combat tactic. Heroes should be able to do it without any artificial metagame limits on how often.
Those with special combat training should absolutely be able to do a better job at it than others: do it more reliably, more efficiently. But even little kids know that if you knock someone over, it's a lot easier to wail on them.
It's redonkulous as a per-encounter power.
It should be a tactic available to everyone.
I've got issues with how they're doing grapple, too. And if disarm and sunder are per-encounter powers or exclusive fighter powers or somesuch, that'll be suck points, too.
Kind of like how it's suck points that weapon finesse is now exclusive to rogues.
Boo and Hiss.