I've been thinking about this feature a lot, too. I like to have the latest and coolest, but HDMI on a phone would be as useful as (looks around kitchen.....) a remote for the coffee maker. To me, HDMI on a phone has potential in two ways; first, to display media that was already on a phone to a high-def TV or monitor, or to stream media from somewhere else to a high-def TV or monitor.
Media on a phone would include pictures or movies that you've taken with its camera, or media (movies, recorded tv, etc) that you've gotten from elsewhere that you're storing in onboard memory or an SD card. Displaying photos or movies that you've captured with the camera makes sense IF you depend heavily on your phone camera (as opposed to a digital or film camera) and if the quality of the phone camera is such that the pictures it takes will be worthy of blowing up to big-screen size. At my daughter's college graduation next month you can be sure the phone will be in my purse and the "real" camera will be out. On the rare occasion that I'd use the phone's camera in preference to a "real" camera it's not too hard to get the pictures out of a phone anyway, as a USB port for a card reader or even SD readers are built into HDTVs and monitors today.
Media files stored on the phone would have to be of sufficient size/quality to make them look good when blown up to HDTV size. I record TV shows on my HTPC, then shrink the files and store them on my phone for later viewing. These files are about 100 MB for a half hour show. I also use Fair Use Wizard to shrink DVDs that we own down the same way - these files are maybe 250-500 MB for a full length movie. Here's the thing a movie (about 250 MB) looked fine on my current phone's 2.8" 240x320 screen, but when I blew it up to view on our big screen HDTV, it looked just awful - not enough data. For a stored movie to fill up the Incredible's screen (3.7", 480 x 800) I'm guessing (someone, please correct me if I'm wrong) it would take roughly 5 times as much data to fill it up for what I'm sure will be a much nicer, sharper picture. But if you use HDMI to watch it on a big screen TV, I'm pretty sure it'll still look bad, unless you convert your media to a much bigger file. Then you'll end up taking much more of your storage space. For my purposes, it wouldn't be worth the trouble to have to keep switching out a few very large files. I'll either watch it on the Incredible's screen, or use a laptop with HDMI out to watch it on an HDTV. Or just use a DVD player.
Streaming video would be stuff not stored on the phone, like watching TV through a network's website or, maybe someday, movies from Netflix. Once again, seeing it on a 3.7" screen, no problem. I'm having a hard time believing, however, that we'd be able to stream data through a cell phone fast enough to fill up a big screen nicely, or that Verizon would allow that much data to be streamed, even with the "Unlimited" data plan. With the faster networks coming maybe the stream would be sufficient, but I foresee tiered pricing because we'd be talking about a LOT of data, and I can't see Verizon giving that for $39 a month. What would prevent people from canceling their cable if they could watch their favorite shows the next day in High def from the network's site through their phones on their big TVs?
To sum up, I don't think HDMI is a feature worth waiting for on a phone, and if people have it, it will eventually end up costing us more in our plans.
