I had several two blade easels and they all shared a common problem. It was really difficult to set the paper in correctly so that fixed portion of the borders are parallel to the edge. All of them had a little adjustable L shaped "tab" to set the corner - that was it. There was nothing to support the long end. The end result was, crocked paper and uneven borders. I gave them away.
I watched the APUG classified closely and picked up a pair of nice 4 blade ones for $50 each. I've been happy since.
On the in-expensive side, I have some fixed hole easels. (the kind it has metal plates with holes on both sides) These aren't adjustable but easy to use, consistent, and inexpensive.