Ok everyone, my take. I have an F5, but I mostly used for news and weddings the F3P+MD4 and F4s, and often used those two in the capacity of a high speed sports camera. By the time I got the F5 I had less use for the high speed aspects, so I then I appreciated the camera for more of the control aspects, which was something I sometimes found challenging with the F4 and F3. The 1/3 step shutter as well as the auto bracketing in 1/3 steps I found useful in dialing a black and white darkroom, but compared to the F4 and F3 the viewfinder of the F5 is much dimmer. I also found the F5 less usable in low light wedding coverage since the there is no way to reduce the in viewfinder light (anyone have a secret Custom Function?) which effectively makes it harder to manual focus. It also could not TTL flash with Manual MF Nikkor glass which the F4 did spectacularly well in a wedding context, and I was very (still am) fond of the Nikkor 35mm 1.4. I found the use of Energizer Lithium AA's to help shave weight, the MS-30 battery holder is more expensive than a whole camera and I still need to rebuild a pair of MN-30's. As I've slowly increased my acquisition of AF glass the F5 is nice to use in AF with G and D series lenses. The F5 remains a superlative sports camera and I include it in the bag to shoot surfing on the North Shore (its tough and weather resistant). As with all F series a screen change for specific lens can do wonders for viewing and focusing, those Nikon engineers designed it to swap out the screens easily. The already mentioned auto bracketing in 1/3 stops is insanely good for very quickly getting a useful range of exposures which is cost effective in shooting slides.
That all being said (sheesh!) I do think that if you can see a need at some point of what the F5 offers then for sure get one, and probably sooner. These were and are expensive yet durable pieces of kit, and the prices are still astonishingly low. But yes: heavy. Ha.