I don't think any AIO has "a lot of problems with leaks". Such products don't make it past QA and if they did, they would quickly receive bad user reviews and high RMA percentages, and possibly force the manufacturer to recall all units as faulty. Leaking is a pretty rare problem. Pump failure or other pump-related issues are much more common, and pose no immediate threat to your components.
Looking at the
240EX specs, I don't see any real downsides. Usually fan noise is a pain with AIO's, but the 240EX's fans seem decent enough with a relatively low minimum RPM, ensuring low noise operation when idling.
What CPU do you plan to cool with it and how far do you intend to overclock?