The rig that I work on is the Sedco 709, she is an older rig and does not have the bells and whistles that the new generation stuff has, a bit like comparing a Landrover to a Land Cruiser.
That said, we work (well most of the time) and that cannot be said for the majority of the new stuff.
709 was built in in 1977 the first ever dynamically positioned (see DP) semi-submersible drilling rig
She is 90 m long and 75 m wide, the derrick top is 102 m above the keel which is 68 m above the main deck (yes it is a long climb).
This picture shows us at drilling draft, there is another 21 meters under the water.