Pros
eBay treats you like an adult and that can be nice if you come from a small company where they are constantly involving themselves in your work. You are given general information and expected to run with it and create a solution. There are some great employee amenities on site including massage and car wash and a nice size cafe. Fun events are a regular happening, sometimes once a week. If you have the right Manager - I do - many of the difficulties will seem less difficult. As far as I can tell, there is only the one so be careful which group you choose. The campus has on site parking (get here early) and nice size cubicles. The outside areas are really excellent and have places for gathering and having meetings when the weather is nice. There are many good places to eat nearby.
Cons
If you are at a senior level, you will not find much to learn here. The opportunities to have design discussions and do work with other designers in your field are very limited. This also means you have almost no chance to mentor a younger designer either. Projects are routinely scheduled to be much too short or way too long. Scoping of a project has not quite been figured out. There will be many things at eBay like that. You will not be able to understand why so many small companies have figured out various communications and project planning and eBay is still trying to get it right. The atmosphere is extremely meeting heavy. Reviews for projects are routinely sent to entire distribution lists making it hard to find out which ones you might actually need to be in. Products are not owned by one designer and the excessive use of external contractors means the section of the site you are working on could have other projects you would not see going on at the same time. Engineering will often find it difficult to make projects as you design them since eBay tries to keep back end developers and cares little about GUI programming. Although testing by researchers is available for some projects, there is no easy to use central repository to help you when the project does not have a long time line, so it is hard to learn from others' work. One of the most frustrating things is the review process, which is both very, very long and completely useless. Peer reviews take forever to write since you have to convert all text to 'business, values' speak. The majority of people will come out as 'average' and when someone does over perform, they often do not deserve it and seem to get the promotion not for actual innovative work, but for making up some 'new' way to design, or some other 'outside your usual job' type of project. This means the designers hoping for promotion will 'phone in' their projects and reserve their energy for these extra projects that don't translate to a better UI on the site. If your goal is to make the site easier to use for the actual users, you will be disappointed at your inability to get your designs through the review process. Which is extensive. Further they have jumped on the patterns bandwagon a little too hard. If you have a design out of the pattern, extensive justification is required. Although you might think this makes the site more consistent, it doesn't. And it makes you avoid innovation.