I've only had mine for a couple days, so bear that in mind. I can't really say much about the durability of it.
This is my first 250C mod, so when I say that I fuckin' love it, the board itself is mostly responsible for that. Evolv's boards have been my absolute favorites for almost three years now, and the 250C takes everything that I love about their boards and makes it even better.
As far as the mod itself goes, I waited for this one because it's the only 250C mod out right now that ticks all the boxes for me. Non-lipo, dual battery, can accommodate a 30mm atty without overhang, and I really like the look of it. From the shape, to the textured look, to the unique button setup. It's just a good looking mod.
Cons. It's made of plastic. Fancy future plastic sure, but it's still plastic. It does kind of make it feel cheap. The texture of it combined with the sleek lines and the deep Boxer "engraving" help to balance that out.
It's not pocket friendly AT ALL. Fits the hand well, makes a good sturdy base for tinkering with RDAs/RTAs. not huge, it's just not a good shape for carrying in a pocket. As a side note, it's actually a little shorter than I thought based on the pictures.
There are a lot of ways for dust and debris particles to get to the board. Evolv coats all their boards with some sort of waterproofing, so it's probably fine, it just makes me a little uneasy so I thought I'd point it out.
The 510 isn't very awesome. It's not terrible, but it should be better. Once your atty's in place the ohms are basically stable, but a tiny bit of a turn in either direction will cause it to fluctuate by a couple of milliohms. This can affect TC performance in some situations. Again, that's not that bad, and most people probably won't notice or mind, but I've had more stable resistance on a mass produced Chinese DNA 200 that cost half as much. It bugs me a little bit.
In my opinion, it's not worth $250. It's just not. They charge that because people(like myself) will pay it. Plain and simple. That being said though, there isn't another 250C mod out right now that I'd rather have. If the mod was gone and I had my money back, I'd buy another one. It's a great looking mod and my favorite tanks look fantastic on it.
Hope that helps!