The thing about Ultrasun is that each of the formulas has a different base. The Gel/Sports 20 is very alcoholic and stinky and the smell is off-putting. The Sensitive Family lotion 30 is great and doesn't smell at all, and I use it all year round in the UK, but it has a matt base that some people won't like as it does give a slightly white-grey tinge (calms down my rosacea a bit). The 50 lotion is great when abroad, doesn't have the white-grey tinge effect and doesn't smell, but it does leave you looking shiny.
All of them work effectively provided you follow the instructions: you have to put them on clean dry skin before any other products and allow them to dry before adding any other creams or moisturisers. You must leave 15-20 minutes before going into the sun for the product to bind properly to the skin.
If you do that, they work - and last for about 8 hours.
If you just rub them on and head off, perspiring into the sun, or add other creams before Ultrasun is dry then they won't.