I've used BattlePing for ages now for World of Warcraft. Basically it ensures all your MMO traffic gets routed optimally and ensures the traffic gets the highest priority on your ISP's network by tunneling it through SSH.
I haven't played Rift before, but it worked very well for WoW, went from 300ms to 180ms. While it did lower my latency, what I found more important than that was the stability it gave. Just a plain ol' shaped/unshaped ADSL connection to EU WoW has regular jitter, spikes and more occasionally a disconnect due to shaping/contention of international bandwidth, BattlePing completely eliminated that. Even more interesting is that our undersea cables often get anchors dragged over them, so the ISP swaps over to HIGHLY contented backup bandwidth, normally killing any plans for international gaming for a bit. With BattlePing because the traffic is seen as high priority, you can carry on playing just fine in most cases.
They have a 10 minute trial you can use to log in quick and see if the improvement (or lack thereof) is worth paying for.
I also use Lowerping for Ultima Online since BattlePing doesn't support UO and that seems to work just as well. In fact UO went from unplayable to playable with a double click =)