Yes, that works for those that installed rootkeeper before the OTA. Some had trouble installing the update though, and some said that root only works on applications that already had root. (But others have reported that root does work with new apps, and I don't know what causes this difference in reports!)
But rootkeeper is only a temporary solution. If something goes wrong when rooted, such as flashing a new ROM that causes issues, the usual thing to do is to SBF back to stock, reroot and do something else. So even if we had an SBF for this version, without a real root method, doing the SBF rubs out all the rootkeeper stuff, and you would be unable to regain root. Of course, not an issue for now, as we don't even have an SBF, and you cannot use earlier ones.
But be aware that being rooted in .621 means you have to be extra careful, as there is no way to recover if you mess up.