After some deliberation and questions I've decided to make a few rulings/statements on some of the things that haven't been discussed in detail.
Size increases: 1 EP = a 50% size increase to both length and width. So a 2 EP expenditure doubles the size of your creature. It is important to note that doubling your size is likely to double the amount of food required to sustain your population.
Mouth size matters. If your species has a 2 inch mouth, it can only fit things up to 2 inches inside of it. Evolving ways to take small bites out of big things (and other such solutions) could help you work around this.
Intelligence matters. Having a smarter creature means it may be able to outsmart prey, or adapt to situations better. I've been thinking about sending out extra info to smarter species (now that we're getting smarter species), but no promises on that.
Senses matter. If you've blind, have no sense of smell or hearing, or other sense, you're already at a disadvantage. Finding food is hard for these creatures.
There are 3 kinds of bioweapon in the game: poison/toxin, venom, and acid. Having a resistance to one does not mean you have resistance to the others. Similarly physical attack matters, having armor and weapons (especially if you're a predator) help take down prey. Right now we don't have a lot of those kinds of evolutions going on.