-soft & flexible
-wide range of colors & textures
-because of all the above, it's an easy way to experiment to find what you like & dislike.
-toxic or questionable chemicals - Ingredients not disclosed or regulated! Nobody knows everything that's in them as there are many different chemical recipes.
-If they touch other jelly materials in storage, they react with each other & melt into a pile of goo.
-Not long lasting - The surface starts to decompose over time.
If you do decide to buy one, I'd highly recommend wearing a condom or toy cover & at the very least, clean carefully using an unscented antibacterial soap,(like Hibiclens), or a 10% bleach solution. If used anally, devote that toy to exclusive anal use. And watch the surface over time! If you notice it's becoming dull, that means it's breaking down & you can't clean it safely, so toss it.
IMO, with all the other, safer options that can be found nowadays, why risk it? I HIGHLY recommend you research the topic & make a more informed decision than you can make just by visiting here. Below are some links to info on the topic:
(--please, if nothing else, watch the video from Smitten Kitten owner on this page!!)