It's fair to say that I am a mosquito magnet, so I spent a lot of time researching DEET-based (and other natural) products before settling on this one. Scientists still recommend DEET as the only genuinely effective mosquito repellent, so if you're travelling to a country where malaria and dengue fever are a problem, you should definitely be looking for something with DEET in it.
Saying that "I love Deet" might be a bit of an exaggeration; however, one thing's for sure, I love being mosquito-proof. I've just used this in Cambodia for 2 weeks, and can say that I've been unbitten by mosquitoes whenever I've worn it. I found it particularly useful for my feet, which were exposed in sandals whilst the rest of me was covered by long clothing: the result was not a single mossie-bite on my feet! (Ants however, seemed completely happy to bite me with or without DEET.)
I was pleasantly surprised that this wasn't really greasy to apply, and dried without any noticeable effects on my skin; there was no strong chemical smell either ... so for these reasons, this DEET spray is great. It certainly worked for the "hours" I was out, usually about 3 or 4 after it was applied.
The bottle itself is made of a robust plastic, so I had no leakage problems despite it being bashed around in my rucksack. The spray nozzle didn't drip or leak after use either.
All in all, a well-designed and very effective product for the traveller heading off for mosquito-infested areas.