The Thermopop is a good device but the rotating display and backlight only work if you press a button.
The Thermopop also reads temps slight slower. With that said it's a great device and if your on a budget
it's the way to go. I have recommended that device to more people than I can count, and they all end up loving
it and recommending it to their friends.
The MKIV is what I have, and the backlight is automatic with auto rotating display, and slightly faster read time.
It feels very good in the hand and is more ergonomic in my opinion. My first Thermopen was the classic and it worked
good but lacked the above mentioned features. You cannot go wrong with either one, and
I would say it boils down to your needs. I wanted those features so I upgraded and sold my Thermopen Classic.