Personally, I've found very few after-market (non OEM) accessories are "essential".
For the Spark I "could" see wanting extended landing legs if one lands in some odd terrain other than smooth pavement, but my solution is to put it in gesture mode and land it on my hand. The MavMount is the only accessory that I see as necessary IF you choose to use a table larger than an Ipad Mini.
IMO, gimbal locks aren't necessary if you use the foam case the Spark came in or a good case thats cut specifically for the Spark. I've put my Spark in the top case of my motorcycle in its foam case and ridden over some the bumpiest, rocky, wash-board surfaces that was like sitting on a jack-hammer and my Spark was just fine.
A couple things I "think" that are bigger negatives with that Silicone Cover than protecting it from "scratches" and Scuff Marks are; Its probably not smooth, therefore will cause more drag on the Spark which in turn means shorter
battery life; It insulates the drone, so it probably runs hotter; Its added weight. Sure its probably marginal, but its still added weight which in turn means a more drain on the
battery therefore shorter
battery life. Agree, what I say is probably "over-stated" or marginal, but those are concerns...
