It's hard to believe, but there was a time when this was the ultimate cutting edge of plug-in reverb, an eagerly anticipated contribution from Waves to the then very limited reverb market. Since then, there has been a big move towards ultra-detailed (attempted) recreations of studio stalwarts like the Lexicon and EMT Plate reverbs, with increasingly pleasing results that have mostly left RenVerb in the dust.
However, the tables have turned, and what was once considered the highest CPU-soaking plug-in (people used to use RenVerb to do DAW CPU shootouts), it is now almost negligible on any modern machine; you can run as many as you like, making this an ideal tracking reverb that you could always swap out for something fancier during final mixing, if you like.
Then again, there are some good algorithms on here, and the interface is very easy to use and understand. Most users needn't go much further then the large choice of presets, tweaking only the "Time" variable to taste, but picky professionals will find all the requisite tools here; damping, EQ, pre-delay, early refelection levels, etc. The "Hall 2" and "plate 1" algorithms are epsecially good, but things like the Gated and Room are less than satisfactory.
Still, anyone who owns a Waves bundle will find this a helpful tool for quick mixing and may even decide to just leave it on once they fine-tune it a bit. It's a classic that I keep turning to, but I do look forward to Waves making it's entry into the proper boutique reverb market!