The shatterproof glass window allows you to keep track of usage. It's approved for use in airplanes and it's completely leak-proof (I used to carry my body spray in a tiny plastic spray bottle but it would invariable leak; my bag smelt wonderful though).
The capacity is only 4ml; this is good for perfumes since you won't use too much, but bad for body sprays since you need to spray more and it won't last. I tried refilling it with my body spray and it lasted me barely a week. Plus, while the method of refilling via the hole at the bottom is very convenient, the presence of the hole means your precious fragrance will evaporate with time. I wanted to get the Travalo to store my body spray for travel (so that I'll have more space in my luggage), but it seems like it won't work for me, because it won't last for trips longer than 7 days.
It's also difficult to 'wash' the Travalo if you want to fill it with a different fragrance - you need to fill a spray pump with water, refill the Travalo with water in the same way as you refill your fragrance, and spray it away. Lastly, it's pretty pricey - I paid S$15 for it.
Conclusion: I'm in 2 minds about it... I absolutely love the fact that it is so reliably leak-proof (my plastic spray bottles always leak in my bag!), but there are so many other cons. I've also seen metal atomisers at Muji (I don't think they refill in the same way as the Travalo; I think they refill in the 'traditional' pump way) that are similarly priced, however I don't know how leakproof they are, but of course they will be easier to wash. Plus the Muji ones are prettier because they don't have the glass window, and they don't have the brand printed on them.
Rating: 7/10 (It's leakproof which is a huge pro which helps offset all the other cons)
Maybe I'll get the Muji atomiser to try someday... but not too soon, it makes me feel guilty when I buy similar things all at the same time. :P
Oh and here's a photo of my Mum's birthday cake I got her, I love birthday cakes!