What are the biggest known issues with SalesInbox and Zoho One?

What are the biggest known issues with SalesInbox and Zoho One?

We use Zoho One across our business and have our Sales Team using SalesInbox. 

What are the biggest known issues of things that aren't perfect so we can ensure we have a process in place to handle these known quirks?

For example, in this thread (https://help.zoho.com/portal/community/topic/what-should-i-be-using-salesinbox-or-zoho-mail) there are comments like:
  1. SalesInbox it doesn't measure last activity in deals if you are sending emails from Sales Inbox to follow up on a deal, that email will not activate last activity on the deal. (Is this true?)
  2. SalesInbox will leave your IMAP connected mailbox in a right mess. (Is this true?)
Or from this thread:
  1. When I send a email from the CRM directly to a client, the email I sent is not visible in the ''SENT'' folder in my Salesinbox. (Is this true?)
Basically, what I'm wondering is "What are the 5 Biggest flaws or areas for improvement for SalesInbox so we can build our sales process around them?"

Thanks,

Adam