After noting the glaring absence in my logbooks of an observation of this pair through my 18", I made sure to observe it this year: thrice. The first time, I really didn't pick up much. I was at Lake Sonoma, a Bortle 4-ish site frequented by Steve Gottlieb amongst others, with plenty of light pollution to the south. The second time, I was at a much darker site with excellent (Bortle 2-esque) southern skies, but the transparency was so-so. At high power, I was able to pick up the several knots of starburst that dot the outline of NGC 4038, and a prominent brightening in the body of NGC 4039. I also noted that the brightness of NGC 4038 has an asymmetric "hole" in it, so the star-forming regions and the nucleus form a sort of ring of light. Of course, this is a piece of cake to see in Jimi's scope where Howard Banich likened it to flying over a city at night and seeing the lights, but it was a joy to ferret this out in an 18" (it is not too difficult).
Third time is the charm. I did see the beginning of the tidal plume that I mention in the above observation. I was at the "Hovatter Road Antenna Site" in Arizona, which I rate as Bortle 3, but the transparency must have been good and there weren't any light domes in the southern direction. Plus, it rises a tad higher at the lower latitude. The plume was barely, but reproducibly visible just off the edge of NGC 4039. This is the tidal tail of NGC 4038. I also sensed that there seemed to be a slight condensation within the plume, separated slightly from the bodies of NGC 4038 and NGC 4039 by a less brighter region.
Clear Skies
Akarsh