I've used SAM Broadcaster since 2005 and SAM Party DJ since 2003.
It the few years I've used it, I have hardly any trouble.
But then again, I've always used SAM on machines that were more than enough to run it and a lot of other things at the same time. Never a problem. On a previous version, I did have a problem with it freezing up frequently on cuts ripped using Vorbis, which were numerous. It was after that, and investing in a larger hard drive, that I stopped ripping into lossy codecs completely. The newest version released fixes a few issues.
The most current version plays nice on my AMD X2 6000 machine with 2GB of RAM. Using it now on this machine.
I did purchase a Dell for the purpose of getting SAM off of my video machine where I need the AMD dual-core and the RAM. It's one of those GX260s with an Intel 2.00P4 with 512GB of RAM. It did well as could be expected for an Intel machine. I couldn't use any DSPs or the included multiband. I usually run lean machines so, it was kind of interesting to see it stumble as much as it did compared to my dirt old AMD 1600 XP+ with 256MB RAM.
SAM has it's issues, but if you know what you're doing and are willing to learn, it's a good product.
I've can't tell you if StationPlaylist is any better or worse. I've never had time to try it.