these really cheap ones not worth the box they come in?
Pretty much, for this type of work anyway.
That one has a sampling freqeuncy of 4kHz when using 2 channels, that's not even good enough for audio, there's a chance you'll be dealing woth 10kHz or a lot more as the frequency of the data so normally I'd say go for 10x that as a sampling rate. But to be useful I reckon 1MHz is the minimum. If you intend to get into I2C or SPI comms later and want to look at some timing then a 10-20MHz sampling rate would be good.
I use the Saleae Logic
And have to say it's about the best $180 I ever spent. But it won't like +-12v on the inputs which you may have if the controller talks RS-232.
So maybe the best thing to do is wait until you get the controller and determine the voltage levels of the signals, then decide on the best test equipment to get. It also matters what (if anything) you plan to do in the future. If you're into audio then a CRO is a better choice, but for playing with uCs a logic analyser is better.
Rob