I'm pretty sure you could also do this in kde3 / konqueror... the problem I've had with the new version in dolphin is that when you switch tabs it does not always cd to the new directory automatically like it did in kde3 (In kde4 it seems to work for all tabs but the first one opened

) ..I'm sure it will be fixed in the next release.
Split folders is also more flexible in konqueror ( 3 & 4 ).. you can split into mor than just two panes; the one advantage dolphin has, it that each pane has its own URL bar so it easier to tell what directory each pane is showing.