I'm sold. I'm doing it. Moved my radio over this weekend to make room for the IFD. I was on the fence of just doing the 440 but I figured I would regret not having the larger screen someday.That took a little getting used to but it’s not a big deal. If you use the keyboard it is very much like having hard buttons. You can also use the touchscreen. When I know I am about to get a code I press the left knob twice and it displays the transponder code so it can be changed. I either use the touchscreen or the knob to set the code. It takes a tiny bit longer than a dedicated transponder with hard buttons for each number but it’s not a big deal.
I also set one of the very top row datablocks to transponder status so I can always see the code and what mode it is in. This helped me out one time when a friend accidentally switched it to ground mode while entering the code.
As you can see I still have the Stratus transponder. I'm going to pull it out later and install the AXP-322. I'm going to replace the KX-155 with a slimline radio. Then I'll have the full right side for a 10" ipad.