Others have mentioned it, but I'll repeat those thoughts. A poll isn't the end all be all, methodology is important, as is recognizing the limitations of the methodology. So more thought needs to go into looking at a simple online poll to parse our meaningful conclusions. And as was stated, the middle option is very ambiguous and I've already seen it being taken both ways. Ranges on options and even multiple questions on various topics would be a better way to go about it, but even with the 3 options the middle should have been something like "No strong opinion either way" if we were trying to just make some sort of general community feel on the topic. It's also a singular piece of content being parsed and doesn't give a good reference. For example, it would have been interesting to have similar polls for Diadem, PoTD, etc. when they were relevant to draw comparisons against to get a feel for how new content is generally received.
With that said, going with the assumption that the numbers reflect the community within a reasonable margin of error and that the "Meh, it's ok" crowd is more of a "No strong opinion either way", the numbers look bad at Eureka being well received. As of this post the poll stands around 4.2k votes. The numbers of people who either hate it or love it are near identical, while the no strong opinion crowd wins out. It seems like for every 1 person who loves Eureka there is 1 person who hates it. Which means people who say the "hate diadem"-crowd is a vocal minority are wrong. Not everyone hates it either of course. But there seems to be a lot of in between people. Overall I'd say player response to Eureka is not good if the majority of people are in a low-energy opinion on the content. Meanwhile, there is just as many people who detest the content as there are people love it. Again, if the new content has that many people who actively dislike it that is saying something about the content. The bottom line is this content is very divisive and not just on the forums of people actively discussing it.