Justice points are going away forever, perhaps as soon as next Tuesday. You can hold onto them and get the gold conversion if you want. They'll net you 47 silver per point, or 1880 gold for a full cap of 4000. It's a decent chunk of change, but there may be a few things you want to purchase with them while you still can.
The most obvious one is heirlooms. PvE heirlooms will be unavailable from the justice point vendors in 6.0, and your only option to get those will be to spend Darkmoon Prize Tickets at the Darkmoon Faire or Champion's Seals at the Argent Tournament. These heirlooms will return in another form sometime in the future, just not for 6.0.
The one you may have missed is the Reins of the Wooly Mammoth mount sold in Dalaran. If you're trying to pad your mount collection for the collection achievements and you still don't have this one, it's a good way to spend your points. It costs 2175 justice points, or a little over 1,000 gold after the conversion. Once 6.0 hits, this mount is going to cost 8,000 gold instead of justice points. Now is the time to get it.
The last thing is useful if you didn't play much at level cap during Wrath of the Lich King. The commendation badges for the various Wrath reputations are being removed completely. They only cost a mere 16 justice points for 520 reputation points and are also sold in Dalaran. There's badges available for Wyrmrest Accord, Sons of Hodir, Kirin Tor, Argent Crusade, and Knights of the Ebon Blade. It's a quick way to get exalted with these factions. Again, there are some mounts you may be interested in from both Wyrmrest Accord and Sons of Hodir which require revered or exalted reputation. It's certainly quicker than grinding out those reputations the old fashioned way.
All other items which currently cost justice points should cost gold in 6.0, so you don't have to worry about missing out on any potential transmog opportunities.
Filed under: Mists of Pandaria