I mostly use it as the foundation of the ruleset I use when I run Masquerade using Requiem rules and in this regard I find it a solid product, although it does bother me that a few things were left out or given little love.
Specifically, the Giovanni clan weakness isn't discussed at all, which is a shame. Moreover, the author dismisses the idea of the Tremere as a clan, claiming that "the Tremere don't really work as a clan in Requiem", thus presenting as playable choices Tremere as a sect and Tremere as a bloodline. I feel that this really doesn't do them justice.
My biggest concern, however, is with the way the conversion from Generation to Blood Potency was handled - or, rather, should I say, handwaved. While the "Blood Potency system to represent Generation" idea might be reasonable for neonate characters, the system quickly breaks down for lower generation characters: as written in the Translation Guide, every 7th Generation vampire - including a fledgeling embraced two years ago - would suffer from the Methuselah's Thirst. This clearly makes for an unplayable rule in the sense that it would not give rise to a self-consistent world.
Some discipline resistance rolls (specifically Voice of Madness, Total Insanity, Eyes of the Serpent) ought to be errata'd, since related dice pools are formed by combining two attributes and supernatural tolerance, which is kind of an anomaly in the new World of Darkness ruleset.
Lastly, the writeup for Vicissitude Horrid Form is a little unclear, I believe. Masquerade's Horrid Form featured, among other things, becoming bigger (as in eight feet), while in the Translation Guide there is no mention of a Size increase. This is a little ambiguous, since it doesn't specify whether a "Requiem-ish" Horrid Form should actually including a stature increase or not.
Apart from what I just mentioned, however, this is a rather solid product and I am really happy with its purchase. Introductory remarks on tone, scope and metaplot capture both games quite well and suggestions about depiction of clans and covenants are usually well-written and compelling; references to third products are meaningful and useful. The writeup for some disciplines - especially as regards Necromancy, Obtenebration, Quietus and Thaumaturgy - is nothing short of fantastic.
I believe that this product truly deserves a 1.1 version, including errata and info to ensure compatibility with V20. Should any of the above stated concerns be addressed, I would not hesitate to change my opinion on what I now consider a masterpiece missed by a hair.
[4 of 5 Stars!]