I saw last night's performance and thought it was very good. As is often the case, though, the update detracts from the play.
For example, when Chekhov wrote Uncle Vanya in the late 19th Century, Dr. Astrov (well-played by Harper) was way ahead of his time in his environmental advocacy. So, it made sense when other characters looked at him as "weird" or "original." However, moved to the present day, his lecturing is commonplace and even cliched, which seriously undermines what should be an important contrast between him and the others.
Also, if this is the present day, why don't any of these people who feel bored and isolated pull out their cellphones? Why does one character complain that he could have been a Schopenhauer, and another compare what's happening around her to a sentimental novel? The answer is, I think, that the play hasn't really been updated but rather removed from any recognizable reality, either past or present.
Still, nearly the whole cast is strong and will undoubtedly be even better by opening. I was especially impressed by Hadary and Katigbak as Waffles and Marina, characters who, in previous productions, haven't made much of an impact on me (apart perhaps from mild annoyance).