1) If you personally don't use electronic rent collection, why not (or why not yet?)
I do and no longer accept non-electronic payments. My tenants either use their banks own ACH ePay solution, or I direct them to use Venmo.
2) If you use electronic rent collection, which do you use and why?
Saves me considerable time, it's quite easy these days, and there is no 'lost in the mail' excuse possible.
3) What features do you like?
Ease of use, saving of time (theme of the day!) and integration with my PMS (further time savings and reduction in clerical errors). For this second reason, I'll eventually steer all of my tenants to use Venmo.
4) What would you change or add to the service you use (or would use if it had this feature) if you could?
For Venmo specifically, I'd like to have an recurring charge option without the need for an API. But I'm using the API on my website, so this really a non-issue (though it may be one for other people).
Bonus question: What else would you (or do you already) automate in your landlording and/or real estate business if you could?
I automate repairs & maintenance, to some extent, using PMS. Still have to show up, of course, in person; but logging the history of the process is valuable in the long-term management of a building or tenant relationship.