Never shopped from Shark Robot before, but they've been running their store for decades.
VG Cats used to have their share of apparel on Shark Robot.

If you wanna get that Jigsaw Puzzle I wouldn't hesitate, they apparently have low stock remaining if you want it this year.
https://twitter.com/HazbinHotel/sta.....29367487610880

Alrighty, I might go ahead and get it then.

I've done some research on the site myself. Though I've never used it, I've found that, based on write ups and responses to the prompt, "is it reputable?" that SharkRobot was mostly well received. I found one reddit user who had a bad time with the site, but their account was deleted for whatever reason. They're also rated pretty low on ResellersRatings, but something to keep in mind is that ResellerRatings in an of itself isn't a trustworthy review site.
Still, when looking into the site itself, and this is just my opinion on the matter, they do have a semi-unprofessional look about them. The about page for example, is a meek 5 sentences long, despite existing since 2005. Still, there's nothing wildly mischievous about them; based on what I've seen there's no major red flags.

The design on the puzzle looks cool enough~

i've shopped and bought posters from them before they're good.

I never got anything from there but it's from the same guy who also runs SNAFU Comics so it's not mysterious.

I shop from them multiple times, and they're very legit.

Edit: looking at what you purchased, go for it. I bought a bunch of merch from that release (t-shirt, playmat / mouse pad, and some pins) and they arrived here... mostly okay? I had issues but I'm pretty sure it was my post office's fault.

Thats where i get all my hazbin merch, havent had a bad experience yet