I qualify to make this comment (ICC + USCF member) so here are my two cents.
- ICC 5-min (not 5-0 Blitz, but the 5-min games!) are about 100 points lower than your USCF rating (assuming you have played enough games/year such that your paper-rating has followed or matched your true playing strength). The closer you get to 2000 (and/or above) they will CONVERGE. In a ways, the 5-min ratings are the best measure because you get "paired" with an opponent (as you might in a swiss) and can't cherrypick people on a seek graph to boost your rating up. Of course, the naysayers out there will whine that this is nonsense because they can't play blitz chess or that their best chess comes out when they take their time per move. Sure, I can counter-whine about how chess strength correlates with pattern recognition, but sure, that's for another thread :)
- ICC Slow/Standard is about 100-150 (truly inflated) points over the true USCF Rating. Once again, above 2000, the two start to converge and I've seem most titled players (IMs, NMs etc.) with about the same USCF rating as their ICC Slow rating. Once again=> This is true only for those players who have played a *LOT*.
Can anyone who has played at ICC and is a member of the USCF with an established rating tell me the approximate correlation between the ICC Standard Rating and USCF OTB rating, it is, I know, a question that can't really be answered but it is based only from curiosity. It seems to me that ICC ratings are inflated by 100-300 points.