I've never given it more than maybe 5-10 minutes worth of thinking about it before I move on to wanting to do something else, or really just about anything else instead of it. I think just about any decent product will look great when it's brand new, obviously, but what happens after a few months to a year or two? I've admittedly never had SeaDek or any other sort of foam mat product on any of my boats but a few pros and cons are listed below...
Pros: looks nice when new, supposedly it's an anti-slip mat, comfortable on feet/joints, supposedly doesn't get too hot, could increase the value of the boat, probably cheaper to install the first application than having the non-skid redone on your floor, the products that have the snaps on them as well as the medium strength adhesive seem much more practical.
Cons: after a few years I'm assuming the color is going to fade and or the mats will sag/distort, might become slippery when blood or fish guts and so on get on it, you have to clean it constantly from what I've heard so that it doesn't stain, a nice set of flip flops or sandals to wear would be just as nice on your feet and cost way less, if your boat sits outside year round then how long will it last?, it could hurt the value of the boat if you listed it and someone didn't want it on the boat, it's not cheap to do and especially having to do it potentially every 3-7 years or so depending on the product as well as custom designs and panels that are custom fitted only increase the price from there, and the biggest issue that I can think of would be having to tear up the old product to put a new product down. Which I've heard with SeaDek is really a complete PITA to have to do.
If, and this is a big if, I were to go with an EVA foam mat, then I'd probably go with a product like Marine Mat where they have the snaps on the corners and a medium adhesive to where it can be removed fairly quickly and easily as opposed to spending hours and hours and hours to peel everything up and go over it with a product to get all of the adhesive off of it. Depending on the product you buy, I've seen quite a few of them from $2k on up to over $7k, and for something that might get me 5-7 years and could possibly be a PITA to take off when I replace it? I'll spend that money elsewhere. If it was something that would last 10-15 years, was easy to take off or replace if you wanted to and so forth, then I might consider it a bit more. Even if it was slightly more money, as long as the longevity was there then I'd give it more consideration, or if my boat had an issue with the current non-skid on it. At this point, the floor on my boat looks great and even spending around $500 or so wouldn't likely make me want to buy anything like it.