I have been using smart fueling for about three years now, during this time it has worked very well at keeping track of my consumption so as not go over budget each month! The software also syncs across multiple devices such as phones/tablets etc which makes life much easier when traveling or away from home / office! Nothing specific really but perhaps more customization would be helpful like adding custom categories e.g.
gas stations near me (eg Costco) instead of having one default category called 'Gas'. However i don't think there are too many people who will find any faults - if its good enough then why change? Its easy-to use once setup correctly & no maintenance costs involved due to being online 24 hours 7 days per week unlike an oil tank full up every 4 months which can cost thousands.