The only problem I have is how limited the f2p option is. It's very restrictive and I agree with some people here that it is a bit unethical to advertise as f2p while offering a never ending free-trial model. I disagree with many who believe you can't do a f2p model without making it pay to win. There is plenty of non invasive ways of making money while keeping the game generally fair.
True f2p is about being able to achieve the same thing as other people to a point but the difference will usually be in the time you can achieve it. So a person who pays a sub skills up faster, it will take you twice as long as a free player. Many cosmetic options. Cooler looking armour textures, goofy clothes. Whatever. Plenty of other ways without making the game rediculous while turning a profit. Problem with most niche sandbox games isn't the business model, it's because they are crap :P(salem)