I'm late to this discussion, but I agree with the clear majority sentiment here:
Keep the Digitrax, and upgrade it to wireless. I wouldn't use IR for a walkaround system; go straight to radio. HOW to upgrade is the question. If you don't mind the loss of tactile feedback and are OK with using a smart phone as a throttle, getting the Digitrax WiFi interface and running WiThrottle on your iPhone (or an old iPhone you may have sitting in a box from a prior upgrade) is simple and effective. You can put together and break apart consists, and easily access 20 functions with this system. But you won't be able to do ops mode programming (or, actually, ANY programming) with it.
If, like me, you really want tactile feedback and need to access high-number function keys, you can get a UR92 (duplex radio) and DT402D throttle. This will cost a LOT more (in the $300 range for both the throttle and UR92), but Digitrax's duplex radio system is pretty robust and an upside is that you can use the DT402D in wireless mode to do all sorts of programming, either on a programming track or on the main - it can access CV's above 255 (unlike the older DT400's), and I use one to program stuff on my ESU LokSound decoders all the time using ops mode programming.
I do think that the "Holy Grail" of throttles is the ESU Mobile Control: WiFi radio, nice large knob, hard buttons on the side, and a customizable touchscreen for function keys. Unfortunately, right now you can't get the throttle to work fully with anything other than ESU's command stations. If someone in the JMRI project updates the Engine Driver code so that the knob would function correctly, I'd go that route, but I've got too much invested in Digitrax to switch to a full ESU system right now.
John C.