How does the pre 1999 wenge neck differ from the current ovangol neck (not fingerboard)?
Those all-wenge necks made the instruments heavy, and took away some of the presence, to my ears (big boomy rump, tho'). I had a pair of FNA's, in the early '00s, and one (sunburst) had the all-wenge neck; the other (natural) had ovangkol with wenge fingerboard. After swapping the necks, both sounded better, and the sunburst shed a pound of weight.
Of course, both were involved in some horse-trading that led to my FNA 2002 Jazzman LTD (nicknamed "The Shilelagh"), which would have to be pried from my cold, dead hands. There is sentimental value for me in the woods used (walnut back, curly bubinga top, ovangkol neck, wenge fingerboard), since I travelled extensively in Africa, as a boy, and there was a walnut piano in the house where I grew up.
All of that said, I find that I only use my 'wick for very special gigs, and in the studio (which is to say, "not that often"), but my USA G&L JB2 and Squiers go everywhere with me.
Warwicks are not for everyone, just like anything else, but there are certain situations where you're glad that you have one, and put it to great use.