Nope, not a "must have" but the file format is actually much better and smaller than that version and much better control of what you're doing in the newer versions.
They also offered quite hefty price reduction at one time with that. That is how I got on board with them. Got the freebie 3 but then they offered like 50% off the 5 version so I went ahead and bought it. Then just last week I updated to 6
