I have one and like it. It's a streaming USB (24MS/s, 8 channels, almost unlimited depth) type, as opposed to the FPGA (more channels, faster sampling rate, limited memory, examples are Zeroplus and Intronix Logicport) type. Since you're basically forced to use their software all the time, I think this is an important consideration. In my opinion, Saleae's software is really nice to use, and now the cross-platform version is released, it's regularly updated again. The fact that I can use it under Linux without any emulation was the deciding factor when I purchased it. The streaming USB analyzers don't tend to work well with virtualization, since they depend on max. USB throughput. Occasionally I'd like more channels or sampling rate, if I had the budget, I'd probably get the Intronix Logicport. But with modern serial protocols, 8 channels are often enough, and 8-bit MCU don't tend to communicate at more than 4MHz or so. The main exception is LCD displays, which often have parallel interfaces (HD44780 is just possible, graphical like KS006x is not). I haven't had any issues achieving the max. 24MS/s.
Last time I checked, the Zeroplus software was horrible, Logicport had many features, but felt a bit clumsy, and USBee was mediocre. USBee have rewritten their software (inspired on the Saleae software) since, but I haven't tried it. The bang/buck award goes to the open hardware OLS, but the software wasn't that mature last time I checked. It's hard to beat the $40 or so, however.