Good friends for your Deck!
I got the Deckmate Entire System and couldn't be happier with it. The plastic feels durable and surprisingly strong for being so thin. There are also a couple of really strong features of Deckmate that aren't really called out in the descriptions, so I'll do so here:
First, the case which came with my Deck still fits great after attaching the Grip. It feels like the Deck can start to slide out of the case at a shallower angle with the Grip attached, but I don't recommend holding an open case with the Deck in it at crazy angles regardless of how you've accessorized it!
But most importantly, the attachments are reversible. That may not sound like much — you probably won't ever want to attach your Kickstand upside down! — but it gives those of us who are paranoid about our Deck's safety a little bit of extra peace of mind.
The attachment interface (the side which is on the accessory, not the Deck) is made of two parts: a solid, fixed side which is part of the body of the attachment and a smaller, spring-loaded slider which normally stays locked in place, but is how you add or remove an attachment. The springs feel plenty strong enough, but they still have to be able to compress when enough force is applied; otherwise, you wouldn't be able to detach accessories.
Now, usually the heaviest thing hanging on your Deckmate will be the Deck itself (such as when using the VESA mount), which the springs should be plenty strong enough to support. Still, paranoia suggests that it could be possible for enough weight to be put on the spring-loaded side to disengage the attachment point, dropping either your Deck or the accessory attached to it. Unacceptable!
Fortunately, the reversible nature of the attachment point lets you choose whether any weight at all is put on the spring-loaded side. If your Deckmate is supporting your Deck (VESA mount, wall mount, etc.), orient the accessory so that the springs are at the top (which puts the slider at the bottom), no weight will rest directly on the springs. On the other hand, if you're holding your Deck and the Deckmate is taking the weight of the accessory (battery pack, USB hub, etc.), instead make sure the springs are at the top (slider at the bottom) to again make sure no weight sits on the springs.
Yes, that's almost certainly overkill, but sometimes, that's a very reassuring option to have.