I confirm this. I used Whizlabs for both SCJP and SCWCD.
Actually SCJP was quite the same as the real exam, and SCWCD is even closer i think.
For example, i took Whizlabs final exam yesterday morning, before my real exam, it took me about one hour and got a 92%. For the real exam, that i took yesterday afternoon, it took me about 1 hour and i got a 95%. So i think Whizlabs is REALLY close to real exam.
About the exam content and organization, it's the same as real exam. If you want to know if it's a good investment, my anwser with two exams/simulators experience is definitely YES.
I think i should send a link to this post to Whizlabs