Now for the issues...not many
First was the pump is not a super tight fit. That's not normally a problem but when its shipped all together like it was it could have caused the volute to crack the acrylic which it didn't the back plate did fall off. Easy fix but shows it should have been packaged separately and better.
The only other issue I see so far is the o-ring comes out of its groove way to easily. I didn't even realize the ES2 had one as it's black and sits in its groove a little deeper and hasn't fallen out at all. The EM300 you look at it funny and it comes out of its groove. You also have to make sure it doesn't get pinched and loop into the inside of the skimmer when putting on the collection cup.
I do like that the outlet pipe comes out and can be repositioned just like the ES2 and allows for very fine adjustments.
Now to see how well it breaks in and performs. In the future I would be interested in fitting the shark 3 pump into the SRO3000SSS. The bb hy3000 seemed to be a bit to much for the body. The shark drawing in a very good amount of air but slightly less then the hy3000 might make for a great skimmer. I'll still hate that press on plate on the bottom though. Or I would also like to get a hold of one of those aquamaxx cones Q3 plates and put it into the EM300. After seeing the EM300 in person I'm disappointed in the reduction in size of the Q series. Time will tell for everything though.