Pros
Work/Life balance was good (40 hours/week), PTO is at industry standard, benefits are standard. You are doing exactly what the client scientists are doing (for sig. less pay), but you can get good experience if you can sell it to another employer (I found it to be a hard sell, greater than >2 years in contract work may have been impossible unless for another contract position)
Cons
The Professional Scientific Services (PSS) is the wild west; you are playing Russian Roulette on your work experience/career by taking a position in PSS. You are completely at the mercy of whomever your clients are, with no chance to screen the people you actually will be working with before you already on site. On the ELLI administrative side; my job description was somehow incorrect, so they hired for assay development work when they only wanted assay validation. I get on site - surprise! This job isn't what you were told it was! These two activities are very different, so either the ELLI hiring staff and/or client are grossly ignorant about what the position even entailed.