Ah, feat creation. I echo the previous thing about deciding the 'balance level' of your feat. Personally I go for useful but not too useful feats like power attack. They do their job and they do it well. You may want to find a feat which closest resembles the one your creating, to compare and contrast. Sometimes feats I'm making are outright replacements to feats I think are too weak or too strong. In this case you don't need to compare it to its source material but rather to feats of a balance point that you desire.
There are no hard rules, only guidelines. Your feat should do the following:
A) State your goal clearly. Your goal's power is based on whatever you're comparing it to. You can either be expanding options (a horizontal change) or improving an option (a vertical change). Horizontal changes are easiest, vertical changes you should be aware of potential stacking and abuses.
B) Figure out what level this feat comes online. If the feat is intended for level 7-8 and up, consider what you'll be facing there, both in enemies and what your allies are doing. Adjust the strength of the feat accordingly, or change when it comes online.
C) The best feats are always useful. Ask yourself if there are any levels that the feat stops having a significent benefit.
D) The last step is just looking for loopholes and abuses, and other unintended consequences. Particularly with feats, usually anyone can take them of any class. You may have intended your feat for fighters, but better check to see if wizards can use this to generate some negative unintended side effect, and so forth. Also here, checking your language for poor or unclear wording. Break out your black hat and try to break your feat.
Follow that and you usually have something compitent at the end of it.
Lesse...
Accomplished Researcher stuff...
Not bad, and compartable to Expanded Knowledge on psionics, but as Jack brought up it has very unintended consequences. It is straight up better than Extra Spell, but I don't think that was the intended balance point. It's closer to Expanded Knowledge, but lacks the "you get a spell one level lower than the highest you can cast" text, so it's actually stronger than Expanded Knowledge too.
One way to handle this is to seal up the feat, limiting it to the spell lists of classes X Y and Z. While it doesn't have room for growth, it cuts off abuse that Obscure Class W has a spell list with Time Stop and Shapechange as 1st level spells and whatnot. You know what you're getting.
If you want to lower its strength you can add back in the "1 level lower" text again. You can also add requirements to the pre-reqs or have some sort of downside like an extra component, cost, etc. Too many downsides and it would become unbalanced though, and no one would take it. You are spending a feat after all, so it is worth something.
...ah, I just noticed, this feat seems to give you benefit over your entire career. Thats stronger than I anticipate, and I personally discourage it (though, it doesn't make for a half-bad ACF).
The idea of the feat is just fine though, I like it. Needs tightening, but the concept is sound. Of course, it was just a hashed out quick example, but you get the idea.
Does that help?