The GR 7 splits into a Northern and a Southern variant in Andalusia. I had chosen the Northern variant for the simple reason that it is lower and I was hiking in winter. From what I could see of the Sierra Nevada in the distance this has been the right decision for me: there has been plenty of precipitation and therefore plenty of snow in the Sierra whereas I had not encountered any snow problems on the tramo Norte.
Also the landscape is not really that exciting: There are two good bits: Cazorala National Park and the little Sierra Magina National Park. And although they are very scenic you are hiking through them on forest roads. You are almost always on forest roads or dirt roads anyways. Plus the GR 7 in Andalucia has a high percentage on pavement walking. The roads are not very busy, but still bad for your feet. And you don't want to be on single file trail anyways because it is so neglected and overgrown that you won't find it. What you will see more than you ever wanted to see is olive trees. 28 million of them in the province of Jaen alone. Nothing against olive trees but two weeks of them is too much!
Even the cities are not that great: Alcala la Real and Priego de Cordoba are real highlights, but other than that the trail towns are nothing special. Not bad either, but nothing outstanding. I was much more impressed with the trail towns in Valencia.
Don't get me wrong: the tramo norte is not a disaster but if you don't have a compelling reason to hike it there are much better alternatives.
If you want to thruhike the GR 7, then choose the Southern variant.
If you want to hike in Andalucia in the mountains, I would highly recommend the brand new GR 247 "Bosques del Sur".
If you want to hike in Andalucia in winter and avoid high altitude, try the brand new GR 249 "Gran Senda de Malaga"
If you want to hike just one part of the GR 7, hike the section in Valencia. Much better marked, fantastic landscape and trail towns and a lot of single file trail.