Indeed the Opus 5 was the darling of PuristS for a number of reasons.....mostly tactile.
1) It was a "new" variation of reading time display, with antecedents from Audemars Piguet Starwheel. The rotating cubes instead of truncated cones was the 'novelty'. You always try to touch the cubes.
2) The case is wonderfully tactile, all that machismo curves and smooth metal with knobbly bits and arches...lovely!
3) Opus 5 touched the watch lovers because it actually worked (unlike the Opus 3) and proved that Harry Winston Rare Timepieces (as it was known) could produce haute horlogerie where the movement, dial, case etc, sparkled more than diamonds.
Regards,
MTF