I've been using Zeroplus for many years. It was my first logic analyzer, so for me, it was OK because I could find everything I needed to do by reading the manual and spending time with the software during the initial learning curve phase (actually more trial and error than reading the manual). After you get used to the software, having access to over 100 serial decoders, makes it difficult to switch to other logic analyzers. Later I tried saelig, and for sure the software is easier to use, looks nicer, but functionality is basic compared to zeroplus. Recently I got several HP and Agilent logic analyzers, and doing timing analysis is way better, but serial decoding is painful, even in the "newer" 16801A. Agilent added i2c and SPI decoding, but only in listing mode and each decoding is shown in separate columns.
In summary, each device has PROS and CONS. Zeroplus is nice for serial decoding of 100+ protocols. Old school Logic Analyzers are good for timing analysis and some vintage CPU disassembly in state mode.
The zeroplus LA was hackable (from the basic 16 channel 32Kb memory model to the full 32 channel 2Mb memory model) by adding the resistors, caps, the input buffer and switching the SRAM, and changing the device ID through USB, but I think the door was closed many years ago.