I like the gobetwino because it seems like it should be a pretty straightforward program that'll take data only when i send it, so not overwhelming.
There's a few other data logging programs out there aswell, I found this one late last night that might be what you are looking for:
http://timewitharduino.blogspot.com/...o-or-read.html
and basically most things on the arduino interfacing with software page:
http://arduino.cc/playground/Main/In...ngWithSoftware
I used to do PLC programming as well. I took a Jva course in college a few years back, never really used it too much until recently. I've been doing lots of VBA programming at work, and now with the arduino i've relearned C programming. Like you say, fun experience so far, can't wait to see what my controller ends up as.