a lot of people experienced this:
you start the game and are happy to farm some more awesome items - but for the first minutes, the lag is killing the mood.
short answer: the loading of d3 may be quite bad. i got an SSD today, it is 100% gone - smooth gaming from the first second.
a lot of people have posted this, mainly on the official forums and i think there is a thread here, too. the annoying lag is just loading from your harddrive.... everyone with a decent pc will have predicted this, but i thought i'd post it anyways. my old harddisc with ~60mb/s effective data loading just didnt cut it. you can test this with any free tool out there.
well, i got an ssd and put my d3 on it - and it's like magic. it's so awesome, i just had to share this =)
the loading of d3 is really off somehow - but there is a solution. ssd´s are not cheap, but they will improve and maybe revolutionize your computer-experience. this does not stop with d3.... windows in general is so smooth now. HDD-loading was preventing so much performance, i cant even tell you...
well, i'm not paid for this but i thought, i'd share it really quick.