The basic premise behind the site is sound. They run a Database of foods and the corresponding caloric and nutrient values and plug into exercise services (Like Garmin and Strava) for access to energy expenditure data. You eat, keep track of what you're eating, keep track of your exercise or energy expended and manage your body weight accordingly.
That, in principle is valuable and so worth money, we can get into how much another time.
There's a problem though. The database is unverified, there are many versions and iterations of the same foods in the DB and they tend to reflect different caloric value for the same food. The reason this is the case is that the caloric values of foods are added or captured into the DB by the community and, saliently, not verified by the provider. The implication is that it's a gamble, if you're lucky you'll be keeping a more or less accurate track of what you're consuming, if you aren't lucky then there's no value here over just reading the packages each time you make a meal.
If you feel this is easy to overcome I need to point out that, if, in trying to overcome this shortfall, you assume that the highest value for a particular food is true then doing that will help you to lose weight, although probably too fast and in a way which is risky. If you assume the lowest is true that'll help you to gain weight, but if you're body building then you need more than just to know the caloric value, the proportional protein content for instance will be among important information you'll need. Anywhere in between is exactly the same as guessing based on reading the packaging.
Because we're tracking a few moving targets (Daily intake, proportion of fats, water, protein, sugars, salts and so forth, energy expended from exercise) it's important that they all be as accurate as possible. Success is directly proportional to accuracy.
If you're thinking "But that's fine, it needn't be all that accurate", then I should point out that variance need only be twenty five or thirty calories per meal to make a material difference in progress. Even using the finer grained kilojoule measurement (4.14 Kj per Calorie, so 30 Calories is 124 Kj) If you're trying to eat 5800 Kilojoules and you miss that by 124 three times a day you're likely to very slowly gain weight instead of losing it.
Where that leaves the provider is that they need to provide a high accuracy service to be more valuable than guessing based on the number on the packaging of food and an estimation of the portion size taken from the package.
They make some marketing errors too, there isn't enough differentiation between the free and paid for service, which further weakens the argument for the paid for service. The sales technique is offer the free service and then move you to the paid for service. The move is encourage by making the claim that more people see success from the paid service than from the free service. The same flaws exist consistently in both. Support is not great, or even good, requests take a long time to garner a response and so far haven't yielded any remedies which weren't going to be implemented without contacting the support team (Meaning you may as well just leave it). And the Downtime is regular, it happens more than once a month that the service is unavailable. Not during service maintenance windows which correspond with the in-country time zone, just down anytime, day or night, alluding to a systemic failure rather than planned maintenance. It leaves one with the feeling that at any moment the company will bankrupt and the service will no longer be available, and that either litigation or a claim against the insolvent company would be the only chance of getting any remaining money back (So a few p to the £ at best, more likely no refund at all).
It's not all bad, they do plug into all the good services, so if you have a garmin, or a suunto and so forth then you're supported (Not just apple). If they could sort out the inaccurate DB problem (And perhaps use the increase in accuracy as a differentiator between the free and paid services) then this service would be worth money (Again, how much money is still up for discussion). Right now the value you'll receive from the service is equivalent to 0£.