We have the Intronix Logicport at work and it is a very useful tool especially for debugging embedded serial protocols.
It can decode SPI, CAN, I2C, RS232 and possibly more.
It can do this across multiple inputs, which can be defined as you like.
I find the CAN decode is especially handy as it handles the bit stuffing which makes the actual line signalling vary depending upon content.
It is not so good as a state analyser if you want to capture every sequential serial word and post analyse.
If you are happy with only timing analysis it is a damn good buy - compact and no noisy fans, unlike the old HP that I still use at times when I really need a state analyser, or more powerful triggering such as "if - then" sequenced triggering.