I think WebPath is good for additional board prep, but the questions are not written in the same format as the step Q's. So if that doesn't bother you (and I don't think it should), then the Q's can help give you additional information that you may not have run across in your classes. Webpath also tends to write a lot of questions with tons of lab values, and very very few of my actual step questions had such a multitude of labs.
As far as difficulty goes, I personally thought it varied from one Webpath subject exam to the next. I thought most questions were pretty easy, but there would be the occasional one that asked about something completely random and unimporant (my definition of difficult 🙂 ).