I'm actually quite ambivalent about the advent of voice-acting, and I think it is, at best, a mixed blessing. Typically, it's expensive and sucks up resources, and it can also complicate the creation of player-made modifications.
However, I've recently replayed Witcher 1 (the Enhanced Edition), and now I'm playing Witcher 2. One thing I've observed about the Witcher series, the latter game in particular, is that the voice-acting is superbly done. And that is just what I've noticed in the English version; they've also published the game in multiple languages!
Now..CD Projekt is a relatively small company, especially when compared to the likes of Bethesda et al. If they can manage to produce games that are not only well-voiced but are also well-written with an engaging story, interesting NPCs, and beautiful visuals.... then why does the voicing in games from much wealthier companies typically range from lacklustre to appalling? For example, excepting Sheogorath in SI, voice-acting in Oblivion was horrible, and while it has been improved in Skyrim, it still isn't all that great.