Pros
Usually good from technology point of view. Being a multinational outsourcing company, if you get bored with a project, you don't have to change the company just the project (in theory at least). Short projects are good to learn learn new things. Assorted colleagues, not much 'difficult personalities'.
Kontras
Senior title also means less room for salary development later on! Being not obviously a senior, be conscious upon signing (or not signing) your job contract. Demand is yet high for IT professionals, negotiate shamelessly (salary, benefits). Three types of projects. Endless ones (processes and used technology settled for a long time which may not be good in a long term), short ones (like a vending machine - technology varies on a wide scale, may be great or terrible but you won't know in advance; you even may end up cooperating with colleagues from Russia who translate English using google) and internal ones (it is hard to keep up your enthusiasm). Tradeoffs everywhere. The 'old' office is like a huge and overstuffed shed. The air conditioning (oxygen content, heat and humidity) is terrible. The only company where I never had a real team building! (It is an important indicator, if you know what I mean.)