Although I am rather new to the site, I already took quite a liking to it. Nevertheless, the level is certainly low. Personally, I'd like to see the main target of the site being standard university physics courses level (i.e. undergradutate/graduate) which would put it somewhere between MO and math.SE (as Tobias suggests) instead of somewhere between high school and undergraduate (which is IMHO where math.SE is).
Now, this certainly doesn't mean that I want to prohibit other kinds of questions. But some level should certainly be enforced (by moderators and the core group of users) in order to get a reasonable mean and variance for the distribution of the level of questions.
Now, all of this was written with an implicit assumption that TP.SE takes off and become a second MO. If you think this is an unreasonable assumption and also want to have a place for some research then obviously standards for physics.SE would have to be set a lot higher. In particular, all undergrad-level questions and below should be closed immediately (and this is probably an unreasonable request). Also graduate-level and research-level question should have to be asked a lot (but here the question is: who will ask them?; and more importantly: who will answer them?).
Seeing as the previous doesn't appear to be very realistic, the first paragraph then seems a next best goal with respect to quality. Also, I think this goal is certainly attainable. In particular, I will start asking some graduate-level questions that have been interesting me lately.
Note regarding what Peter Shor was saying about the concept of good/bad answers not really working
I think this might be a problem of communication. If there is an apparently wrong answer, don't just vote but leave a comment that says so. It may be clear to someone knowledgeable that the answer is wrong but other people might not see this (except as a downvote which can be lost if the question has a few upvotes already anyway). With the comment present, this can be resolved very quickly and it also gives a hint to others to be cautious around the answer. In the same spirit leave a comment letting the others know that some answer is good. I know this is not really democratic but this site has to be built by a core of knowledgeable users. Their votes must count more than votes of someone who knows next to nothing about physics.
Second thing I noticed is that OPs don't really care about accepting good answers. But why don't they accept it? Was it (in their opinion) not all that good and/or didn't they understand something? Well, then they should obviously leave a comment addressing the issue. Or do they think that no answer to their question is even coming close? Well, then they should update the question so that everyone can see what's in their head.
Eventually, there must always appear an answer that is good enough to be accepted (given that the community knows enough about the topic and the question doesn't turn out to be an open problem; both of these conditions are usually satisfied). But if OP neither accepts an answer nor communicates then I take this as a complete ignorance of someone's work (especially when the answer is good). Why should anyone bother answering them? More importantly: why did the OP ask the question in the first place if they don't really care about getting an answer? This behavior appears quite worrisome to me. And no, I am not talking about not getting 15 pts of rep, if anyone asked.