I'm using this device and it works as advertised, no complaints.
Checking around the various forums is good advise as the consensus seems to be those who own and use one are happy campers but their are those who have other preferences which is fine. You'll get similar opposing points of view on pipes, cams. headlights, throttle bodies, polish & wax, tires, seats, paint color, handle bar height, suspension parts, speakers, amps, etc, etc, etc.
Do your homework, speak to each MFG's tech support folks and get what "you" want to do the job. I recently saw a You Tube video where a Fi 2000 was added and digitally measured after a full tune was done by a well known Tuner with a very well respected device and the results were the Fi2000 was still making real time fuel adjustments throughout persons ride. Call Cobra I'm sure they'd be happy to provide the link.