I was already using IFTTT when I found Zapier, but was immediately impressed that the latter seemed serious about tackling the more business-oriented apps. There are several services to help me integrate the usual suspects of Twitter, Evernote, etc. Less common, however, are pre-built connectors for, say, Zoho CRM.
That's really our biggest difference (which I forgot to mention). While we do support some more consumery apps our main goal is to help businesses operate more efficiently and less painfully. When we think about new features, new apps, new services it's almost entirely with a business user in mind.