currently, i want to hook up my micrologix 1500 to ethernet but i am not interested in spending the money to buy its own brand interface.

there are some RS232 to ethernet converters in the market, will these work for this purpose? if it does, what are the criteria in choosing this option?

They'll work... if you can set them up. Some users think the $$ for the A-B unit it worth the lack of hassle inherent in configuring the 3rd party devices.

You will need to use a "COM Port Redirector" utility to have your computer intercept calls to it's serial ports and direct them out to the devices.

I prefer Lantronix, but B&B's stuff has better speed specifications.

You will NOT be able to use the RSLinx Ethernet driver or send messages to the MicroLogix from other PLC's.