I have been wearing Earth shoes for three years and there is definitely a difference. They take a couple of days to get used to, but well worth it.
Since buying my first pair of Earth shoes for work I have now replaced all of my shoes with Earth shoes (gym/running shoes, sandals, boots, casual, dressy). I highly recommend them and will now wear nothing else. They are extremely comfortable and do help with posture.
My best advice for choosing a pair of Earth shoes is to go into a store that sells them, try them on to get your size (I wear a 1/2 size larger in Earth shoes), and to see if you like the look. Then go home and search for them on eBay, amazon, etc., until you find a great deal--they can be expensive!
Most of my Earth shoes are not vegan -- I think only my sandals. Many of their shoes come in "vegan" but also can be made of leather. I always choose leather and leave the vegan shoes for the vegan people.
Bottom line: they are comfortable and the best shoes I have ever owned.