I'm not quite at the point in my process that I'm sitting down for FL's, but there's been a fair bit of discussion about this. Ask different people, you'll probably hear different responses, with the consensus being that no FL can completely capture the tone, difficulty, and overall "feel" of the actual test.
That being said, all practice is good practice! Based on reading a number of threads on this topic, it seems like the NS ones get fairly decent reviews, along with EK, so I think I will use a combination of them. Keep in mind that some FL's (I think I've heard this about Kaplan or TPR) are pretty deflated, so don't put too much stock into your numerical scores there. Use them for practice, to get pacing down, etc, but understand they all have some shortcomings.
But yea, to answer the question, I think the NS and EK ones get pretty decent reviews.