Also, to state the obvious. As was pointed out elsewhere, the developers inadvertently left a kickstart code present on the s3 that allowed one to add any eSATA drive (not just the approved Western Digital ones). TiVo chose to leave that be (as the horse had already left the barn). They did close it later for the TiVoHD. Given that this aspect will torpedo their sales of the Pro model (which only differs in the size of the internal HD), I'd wager that tivo will push an update to units to close this. Folks would be wise to perform this drive upgrade as the very first action they take with a newly received unit, as after going through the Guided Setup, a unit will take a software upgrade, and that will write the new software to the Flash boot disk. For the Roamio/Series5 units, one you take an upgrade, there's no more "rolling" back the software (as was possible to do with the series4 and earlier hardware). Note that I'm speculating that tivo much roll out such an update. Speculating. (though reasonable speculation given how much revenue they may stand to lose).