Hi sinistre,
Thanks for taking the time to let us know what you decided and for sharing your comments and feedback … I appreciate it.
As you know you made a great quality/value choice … and congratulations on your new mattress 
Unlike most innerspring mattresses … most foam mattresses (latex foam, memory foam, or polyfoam) don’t have (or even really need) edge support as long as the firmness of the support core and the thickness of the comfort layers are suitable for your body weight when you are sleeping. Foam mattresses will generally feel softer and compress more deeply if you sleep with most of your weight on the very outside edges of the mattress or if you sit on the very edge of the mattress because your weight is more concentrated when you are sitting than when you are sleeping on the mattress (see post #33 here).
While there are always exceptions … in most cases and for most people this is just a matter of getting used to a foam mattress (particularly if you are used to a spring mattress with edge support) and perhaps sitting a little bit more towards the center of the mattress rather than on the very outside edge.
I’m looking forward to any additional comments you have the chance to share over the course of the next 114 days.
Phoenix