You can take it one step further and add the original email address (the domain one) as a “Send mail as” address under Mail Settings > Accounts and Import. This means that when you reply to an email you received at that address then it goes back from that address. This means that people feel more secure too, as it’s always odd to send an email and have it replied to from a different address – and sometimes somewhat suspicious.
Ultimately, it boils down to a balance between cost, features, and risk. It's always tempting to simply jump on the lowest-cost solution, but the fact that email is ubiquitous keeps this from being the smart play. It's nearly impossible to escape using it, which means your users, your customers, and the guts of your business have all come to depend on it in different ways. You need to discover those ways, evaluate them, and then choose a service that either meets or improves on them. This takes time, discussion with your IT staff, and some investigation; these are steps you don't want to skip. Otherwise, you'll pay for it later.