Sekai Project is pretty notorious in the VN community for having pretty poor translations and quality checking, on top of very shady business tactics such as using Kickstarter to "fund" translations that have already been completed. Their Kickstarter goals are always needlessly excessive, as well. Furthermore, they have published some rather low quality games which has hurt the reputation of VNs in the west. All in all, not a very good company, but unfortunately one with a lot of blindly loyal customers. In comparison, MangaGamer also publishes a fair amount of VNs but their standards for quality are much higher.

Things that Ephidel said, plus butchering VNs(taking away important parts of the plot for no reason), agressive stance towards fantranslations, "proffesionally" translating games that are already fantranslated(and far better), lots of epic fails when it comes to shipping(when shipping some game(i don't remember which one) to australian backers , they chose ANTARCTICA instead of australia, so the games went to penguins... it took them some time to fix this).
The only quality game i know from them is Root/Double.
I hope they will go the same way as Mangagamer and take some time to fix their attitude... but it took Mangagamer years to realise, that being a big bad corporation is bad for business, so i don't expect Sekai Project to fix themselves any time soon