Every time a new smartphone comes out, especially from HTC, someone complains about its lack of the legacy 3.5mm stereo headphones jack, but if you look at the reasoning behind HTC's alternative ExtUSB port, you'll see that what they did is much better.
First of all, every smartphone needs a plug that allows you to recharge the battery. It also needs something to provide data transfer with a desktop computer. And finally, it needs a way to do audio input/output. That's 3 primary functions for an external wired port. The 3.5mm jack can only support one of those things. That means you'll need a second jack for the other two, which also means the device will have to be that much bigger.
HTC's ExtUSB port takes care of all wired external input/output needs all at the same time with a single port that's half the size of the 3.5mm headset jack! In addition to saving a significant amount of space, having only one port that does everything also increases usability. When I want to use my Touch Diamond in the car, I plug in one wire that does both battery charging and audio output to the car stereo. That's one thing to do! With my XPERIA, I have to plug in the USB charging wire on the side and then plug in the 3.5mm headset jack into the top. It's terribly annoying and time consuming.
Of course, the downside is that you'll need an often-included adapter to convert your old 3.5mm jack wires to something that supports the single ExtUSB port, but I would much rather have these large ports be removable as opposed to being stuck in the phone itself. Furthermore, you can easily leave the adapters on your other wired connections and simply plug one thing in when needed.
To me, it seems that leaving the 3.5mm port out is the smarter choice in all cases.