Ventajas
While less so today, eBay has been one of the large consumer web companies that has held some prestige as a place of employment amongst the tech industry. It's a stop on a career path that's not going to hurt to have on your resume. There are some very smart people to work with and the environment is generally good - people respect one another.
Desventajas
Ebay has some significant downsides - in theory management has attempted to address them in the couple years since I left but from second hand info it sounds like it has had mixed results. Functions are very siloed - the company works like a machine but the by product of that is that workers generally feel like cogs in the machine with very little ability to affect big change. Not uncommon in companies of its size obviously. Cash comp is on the low side in my estimation, at least when I was there, and stock has gone nowhere but down or sideways taking away much of the motivation that was inherent in that part of the comp package earlier in the company's lifecycle. Skype and other management decisions seemed to decrease confidence in senior management's vision and skillset though there are many new faces now. Career growth was probably the single biggest gripe for many of the talented folks there - eBay hired many folks in at below market rates and wasn't quick to change their tact as the market got very good. As a result, many quality folks left.