Pros
Great products and technology, awesome customer base and community, good benefits A few years of success at Salesforce.com will add lots of credibility to your resume. After a few years you will be highly marketable to Salesforce partners, other SaaS companies and --if you develop Salesforce technical skills-- any company that uses Salesforce as a customer.
Cons
Since early 2013 there has been a massive influx of new hires --including middle and upper management-- from Oracle. This large scale migration of folks from Oracle to Salesforce means that there are teams within Salesforce where the vast majority of the management structure consist of people hired from Oracle since early 2013. In my case, ALL of the managers (director and VP level) on my team came from Oracle within the past two years. These managers hired a slew of folks into our team from Oracle. At one point, 70% of the new hires on my team came from Oracle. None of these new hires were vetted for cultural fit (because they were hired by managers who didn't understand or value the culture) and none of them competed for their jobs at Salesforce. (Ie, only one candidate was considered for each position.) When you land on a team like this one, you don't really work at Salesforce... you work at some weird bastardization of Salesforce and Oracle. You are selling Salesforce products, but you are living in the Oracle corporate culture, which sucks. The Oracle execs running these teams have not embraced the Salesforce culture and they strongly favor hiring unqualified Oracle refugees over hiring better qualified candidates coming from any other company. The degree of favoritism towards Oracle candidates is offensive. Be very careful before you even pursue a position at Salesforce. Outside of San Francisco, the corporate culture is NOTHING like the experience that Fortune magazine describes in their "best companies to work for" article about Salesforce.