If I remember rightly Ospeed uses compression to give the appearance of better speed so if you are downloading something that is compressable then it will seem faster but not everything can be compressed. It also relies on the page you request being on an Onspeed proxy server compressed and ready to go, if not then there will be a slight lag, it also means that any page you visit is known to Onspeed so they can track your usage and no doubt aim ads etc at you.
Was this not already discussed on the forum a while ago? Seems to ring a bell somewhere in my sleep deprived head
