The app's main committer Harald Mue, who doesn't even have the EVO in his possession, together with a community contributor Andrew Robinson (who does have one) have figured out what was going wrong with the EVO compared to other phones and together collaborated on a fix all within 2 days of finding the problem
Hey, wait a minute, wasn't the EVO released the same 2 days ago? Community dedication never ceases to amaze me.
This is the change that did it by the way:
The only prerequisite is, as always, a rooted EVO. You can read about what root means here and get your EVO rooted in one click by following instructions here. Really, there has never been a simpler way to root - you'll be done in 5 seconds.
Update 6/11/10: Infrastructure mode and WPA2 are now supported by the latest release!
After you've rooted, head over to android-wifi-tether's download page and download a version that is at least 2.0.2.pre14 - this is where EVO support is introduced. You can do this right on your phone by going to the above url and downloading and installing the right .apk file.
Sprint's WiFi Hotspot
Sprint offers its own version of the WiFi app, which supports stronger encryption (WPA/WPA2),
while android-wifi-tether only supports a weak WEP. However, Sprint's hotspot app costs $30 a month while android-wifi-tether is free. You're paying Sprint $10 "premium data" per month already, so why not really take advantage of it? I've been using it on my Hero for months, and it's probably the most useful app on the market, hands down.
While being concerned about WEP, I also use a whitelist capability of android-wifi-tether, which only lets through my pre-approved WiFi MAC addresses. While there is a way to get around that too, chances are the dude on the train next to you will not get a chance to do it (really, it'd be quite complicated).
Now, there may still be bugs, but I and many other users confirmed the new pre14 release to be working. Download yours, test it out, and report back please.