Don't fret. It's just the hipster contingent. "He's everywhere, so, he must be terrible." In all honesty, though, I think of it like the Tao; yin and yang. For years, you had these casual fans who tauted him as the greatest comic book artist ever, and, as we know, to everything there must be an equal and opposite balance, so, somewhere along the line, the Jim Lee Hate Brigade popped up in order to counteract that blind fellowship.
Frankly, I think both sides are a bit extreme. I see "top 10" lists all the time, where Lee is the "number one Batman artist of all time." With such a long history, and guys like **** Sprang, Carmine Infantino, Neal Adams, Jim Aparo, and on and on, I certainly don't think he should nab the top spot, but, at the same time, I don't think the guy deserves nearly as much hate as he gets. I will say, though, that I think a lot of the anti-Lee sentiment started up around when The New 52 came along.
He and Johns were largely, sort of, "The Godfathers" of that whole thing, which, in and of itself, was divisive, and Lee was responsible for a lot of the costume designs, which many found overly busy, with all of the lines and segmentation. I will agree with them, in that regard; his New 52 stuff is fairly "one note," from an aesthetic perspective, but I feel like you could disagree with his design choices, without putting the man's entire artistic style on trial.
To compare him to Liefeld, though, is laughable. Personally, I've always been a fan, and I love this figure. Definitely want to track one down, sooner or later.