Our checkers go over everything. They are universally old-timers who aren't that great on AutoCAD but have well-established, logical, ingrained procedures that allows them to over everything from dimensions to coordinates to materials. Its the same mental attitude as found in CAD support people, proceding in a logical methodical fashion rather than a drafting equivalent to modern dance (ie. hopping randomly around the stage ). There's cross checking where information is referenced in different locations; we are trying to get away from that to reduce checking requirements. As things are checked they get yellowed off with highlighter if good. Notes are green (or lead)/red/blue for instructions/add/delete respectively. Once its ready for return to the client it goes to our small QC group for similar procedures, more for checking presentation and layout than technical information.
Since they aren't good with CAD getting them onto an electronic markup system like DWF or PDF isn't going to happen short of executive VP decree and massive training. There's also some paranoia, justly or not, about traceability of markups.
For the tight-turnaround projects (budget in terms of a handful of hours - literally) checking may be abbreviated, or even skipped entirely if the designers are known to produce consistently good work. QC is always done.