I have a garmin with MSN direct.
The garmin is painfully slow at updating, but I've heard garmins slow down over time with firmware updates and restoring it to a fresh configuration will fix that. I'm not quite ready to manually reinput all my nav points though.
The MSNDirect feature is alright. It gives a variety of semi-useful information that people would most likely just use cell phones for now (even if you're limited to something like text GOOGLE or text CHACHA). Using MSN maps, you can wireless send nav points to your gps, which is kind of cool if planning out a trip.
The actual traffic features seem to have a lag of up to 15 minutes behind. Correspondingly, the gps usually won't reroute for anything less than 20 minutes of traffic (it seems). Things like construction/road work do get marked as traffic, so it takes that into account. It automatically reroutes around traffic, but the results aren't instant and not as well integrated in as missing a turn is. The GPS doesn't say its rerouting, your route is just suddenly updated, which could be good I suppose.
It's great for avoiding major events and massive traffic pile ups, but it adds little to a daily commute, where you intuition can probably tell you the best way. Plus, it only (at least msndirect) monitors highways, so it has a tendency to dump you off onto something a little less major, but still just as packed, so in rare instances, it will add to your commute.