Several researchers are skeptical about the database quality, but their argumentation is somewhat unclear to me.
For instance, Constantinides, Jackwerth and Perrakis (2008) (link):
[...] we were conservative because of concerns regarding the quality of the Option Metrics database.
No argumentation here. Then, Van Binsbergen, Brandt and Koijen (2012) (link):
Using closing prices from OptionMetrics for all quantities does not guarantee that the index value and option prices are recorded at the same time and induces substantial noise in our computations [...] For instance, the options exchange closes 15 minutes later than the equity exchange, which leads to wider bid-ask spreads in options markets during this period.
Here, the authors explicitly define the problem, but the WRDS OptionMetrics manual (link) states the opposite:
OptionMetrics compiles the IvyDB data from raw 3:59PM EST price information.
which could actually be a recent change to the methodology, unknown to the authors of the latter paper.
P.S. There's also a StackExchange answer questioning (no pun implied) quality of OptionMetrics dividend info (link) — again, without argumentation.
UPD #1: Found more info on the closing price issue:
Option prices used in implied volatility calculations up to March 4, 2008 are end of day prices. Starting from March 5, 2008 we have been capturing best bid and best offer as close to 4 o’clock as possible in an attempt to better synchronize the option price with the underlying close. Currently all option quotes, except for VIX option prices, are captured at 15:59 EST.