McClatchy  has the article Al Qaida-linked group Syria rebels once denied now key to anti-Assad victories.

Nearly a year later, however, Jabhat al Nusra, which U.S. officials believe has links to al Qaida, has become essential to the frontline operations of the rebels fighting to topple Assad.

I have no idea about the truth of or falsity of anything in the article.  The only conclusion I can feel certain of is that dealing with the Syria problem is complicated.

In the comments on the article are links to two other articles, America’s New Proxy, The Syrian National Coalition: The Many Faces of its Leader, Sheikh Ahmad Moaz Al-Khatib and
Al-Qaeda affiliate playing larger role in Syria rebellion.  I have no more ability to vouch for these two articles than I have for the McClatchy article.  However, taken all together they just reinforce how fraught with danger it is to meddle (or decide not to meddle) in the internal affairs of other countries.

I guess the only lesson to take away from this is to avoid getting too wedded to one side of the argument or the other and keep your mind open to new information.