Yes it's totally smooth.
Only real problem, and it is a software problem, is with iMovie. I have uploaded a lot of small videos into iPhoto with the photos, and iMovie asks when you first open it whether you want to thumbnail all these movies. I clicked yes- big mistake, it then hangs for around 10 seconds every time you open it whilst it thumbnails all the movies.
This is apparently a well known issue with iMovie and iPhoto, both of which are not the most intuitive of software to use.
Apart from that, and it hanging when my external DVD writer could not read a badly scratched disc, no problems. Unless you want to play the latest 3 d games on top settings at native resolution, it will do everything with aplomb.