Some personal experience in hindsight; I owned one for two years before downsizing to its predecesor, the EOS1N:

It's heavy, very, very robust, easy to navigate (if you are used to Canon cameras), water and vapor sealed, has a 150,000 cycle high speed shutter, too many custom functions to be of sensible use at any one time, can (as can the 1N) chew through 36 exposures in 3 seconds (if you're not on cue as to what settings are where and when!) and will keep you focus of attention among the digital brigade simply because the 1V, when it was released, was the definitive camera for those who wanted the best and needed speed and refinement; nothing lacking there. The strongest point though is in the vast improvement to flash metering, something that was sorely lacking with earlier EOS bodies including the venerated 1N (discontinued 2000).

Good examples can be found readily but whatever you buy should be bench tested (Canon's own technies plug in a computer to download shutter cycles, drive information the number of actual exposures (as opposed to the number of rolls for the EOS 1N), flash and overall system metrics e.g. faults, custom function settings, shutter/aperture accuracy. This assumes the techies actually still have these analysers around.

The EOS 5 is a good and reliable performer — until that Achilles Heel, the mode selector dial, breaks. Mine did so twice, twice repaired, still holding, then the lens release button broke (another known weakness for the 5 and 3), that was repaired and still going, but now the back cover latch is broken; I retired the 5 four years ago, using it since 1993 to 2003: it faithfully captured all the scenes on Velvia that I committed to the Ilfochrome Classic process.

Your biggest gripe over time though might be the weight of the camera; it was too much for me (I have small hands and mild dystrophy) after just a handful of bushwalks (the 1N with PDBE1 is a little better). The EOS 3 is no substitute if you need speed, reliability and brute force; but the 1V is probably an overkill for pottering around the landscape, but the same too can be said of the 1N and legions of other workhorse cameras: if it rows your boat and you really want it, there's just one thing to do: bust the bank!