We have a 1984 E30+ and have been very happy with our boat. These boats are well built and sail very well for coastal cruising. The only criticism we have is that there is relatively little storage space compared with other boats of similar size, especially when cruising for a week or more with more than one couple. Otherwise, we love our boat.
Areas to watch for as potential problems include the mast support (ours has been reinforced), the Hurth transmission, lack of ventilation in the forepeak, leaks at stanchions, deck fittings and ports as on any older boat, delamination or cracks in the rudder (ours was rebuilt), engine hours/maintenance (though these unversal engines have a good reputation for reliability if maintained).
As any boat of this size is complex (plumbing, electrical, rigging, lifelines, engine, transmission, etc.) a record of maintenance may be a good indication of what has been replaced and what still needs to be done. And of course, a survey can be helpful, though I have also heard of cases where the surveyor missed important things that cost the owner later.
Good luck!
Frank