You all make me laugh! I'm know there are wonderful natural areas to visit in the northwest and VA too! LOL
The trip to Key West can be a crap shoot, but I've averaged 3 trips a year for the past, oh, say 6 years and only had one really negative experience. The challenge is that parts of the latter southern sections are single lane highways with limited passing areas, so if one is unlucky enough to get stuck behind a slow driver or, worse, encounter an accident that shuts down the road, it can be really ugly. I had one normally 4 hour trip pass 6 hours due to such an accident. My trips typically are in June and November, with another sometimes in early months, so I guess that is "winter".
Time of day and day of the week is also key (ha). Worse traffic is going to be later on a Friday and then on a Sunday afternoon into evening. But, there are some absolutely beautiful areas on the drive which helps balance out any stress.
Oh, and PS, I only used the radar cruise on the campground trip and only on the highway portion.