i am using a IKALOGIC ScanaQuad Logic Analyzer SQ50 4 channel Logic analyser ..
works fine .. very satisfied to debug I2C protocol or UART
but Now, i think it is better to choose the 8 channel Model SQ200 , even with eigher cost ..
example: for NRF24L01 protocole or more complicated protocole
4 Channels are enough to observe serial protocols like I2C, USART, SPI, 1-Wire, RS485, and most serial communication protocols.