Pros:

We actually collected our receipts for the past two years, which is crazy.
Google Drive integration is extremely helpful. My receipts can be stored on WellyBox and backed up on Google Drive.
The support is excellent. Every question I asked (and I asked a lot) was answered.
Because I shared my account with my accountant, I no longer have to do the ping pong we always play.

Cons:

When I synced my inbox for the first time, the receipts took about 5 minutes to appear. Not sure if it's a con since there is a message that says it might take some time.

WellyBox deserves 5 tacos for the overall experience!