Which one?
Some of the Aspire tank designs are more prone to leaking than others. I get leaking more often from the "ET" ones, rarely from the CE5 ones and almost never from the Davide glass ones. (not tested enough of the vivi nova style ones to have an opinion)
Another 'feature' of them is that as the head gets gunked up over time less juice is being turned into vapour and it builds up inside the head until you get to a point where it leaks as it can't convert enough liquid into vapour and floods. You get used to them and get to recognise the "this head is about to die point" and replacing the head cures it. Typically the "about to die" point is when you get little vapour and flavour, though if you draw hard on them or get a tank that's got poor airflow it can happen sooner. also the cheaper clearos can sometimes be mis-threaded. If you don't get the centre post nice and straight with the head and if the heads not being pushed firmly enough into the centre post inside the tank, it'll leak like a sieve.
They're minor issues though and usually I don't have any problems. I use the Davides at home and out and about a lot, and we have our juice testers for the flavours we sell here all using CE5 style Aspires, they're pretty decent little clearos.