Firefox becomes non-responsive for a small amount of time when viewing large (wallpaper sized) jpg images. In OpenBSD 5.4 firefox would block for several seconds. In OpenBSD 5.5 the situation improved considerably but it's still not perfect. The lag persists for a very short but visible amount of time. This "bug" is specific to OpenBSD and not to the machine, as i have tested it across different machines. This issue does not appear with other BSDs or linux (without flash).
Secondly, viewing html video (eg in youtube) continuously lags. The sound is perfect but every other video frame seems to stop for a second or two and then the video "jumps" to the correct frame. This makes streaming video playback virtually unwatchable. This "bug" is specific to OpenBSD again. I have tested this at different machines and the result are the same. Once again, this issue does not appear with other BSDs or linux (without flash). Those two problems are much less obvious in OpenBSD-current's firefox, but, especially the second, still exist. I just wanted to report these issues and not complain. It is obvious that there is improvement at every new release of OpenBSD.