The only issue we have with this product, is that the springs don't keep their firmness, even with the every other day flipping and rotating. The salesperson did actually advise us to go for the "extra firm", over the regular, as he warned us it would soften. Thank goodness for that, as anything softer would've been uncomfortable.
As it was the cheaper of our two favourite options, we went for it, but in hindsight, I would have gone for the costlier option...with the hopes that it would have remained firm for longer.
(Disclaimer, we are not large/heavy people)