Replication: Slony-I vs. Mammoth Replicator vs. ?

HI all, I'm trying to implement a highly-scalable, high-performance,
real-time database replication system to back-up my Postgres database
as data gets written.

So far, Mammoth Replicator is looking pretty good but it costs $1000+ .

Has anyone tried Slony-I and other replication systems? Slony-I is
pretty new so I'm a little unsure if it's ready for a prime-time
commercial system yet.

So... wanted to put this out to the experts. Has anyone got any
recommendations or had experiences with real-time database replication
solutions that don't rely on RAID? The reason why I don't want to
rely on a hardware solution is because we are renting dedicated
servers and we don't have access to the boxes, only to software that
gets installed on the boxes.

Thanks,
Chris