Short answer: I'd say it's safe to wait, particularly because there doesn't seem to be any indication of ASUS running out of units to sell anytime soon.
Long answer: I left a rather long YouTube comment which detailed my first day experience with the Ally which I'll copy below. But the TL;DR is that there's a number of pain points and troubleshooting that you have to go through, especially if you're not doing the standard route of unbox -> initial setup -> download your games -> play.
Besides the "shiny new toy" feel though, I would say that objectively it's still an excellent handheld computer - there's just software bugs at this point that take away some of its shine (that, and however you feel about Windows).
I'm a bit of a tinkerer so troubleshooting (and more importantly, arriving at a working system) is fun for me. I have mine up and running now, but it took a while. I'm confident that months down the line these issues will be ironed out, but us day-one people gotta go through the pains, which I fully expected. Here are my experiences:
First boot-up all the way to the OOBE setup for Windows was fine, until I ran into the wifi connection screen. Pressed the command center button to try to bring up the keyboard, no command center (I think the .exe crashed). Tapped on the screen, no pop-up keyboard. Tried the M1 + Up shortcut, no pop-up keyboard. Rebooted and tried to connect to wifi again, doing the shortcut made the keyboard pop up this time.
Once I confirmed everything was working fine (no joystick to mouse issues) shut down the device and removed the backplate to install my SSD. Attempted to do the Cloud Recovery method and was able to finish the download, but it got stuck on the "Checking..." screen for an hour. Turned the device off and started Googling. Turns out my BIOS was not the latest (v 310 or 315 or 317, can't remember now), and somehow that has problems with Cloud Recovery. The solution: you need to update the BIOS in MyASUS first, and to do that, you need to put the original SSD back in. Lol
Reversed what I did in step 2. Now back on the original SSD, updated all the things in MyASUS under Customer Support > LiveUpdate. I think it updated the BIOS a couple of times, unsure because I just set it aside and let it do it's thing. But it took a while and a number of reboots. Once it was done, shut down the device again, then powered it on while pressing the Volume Down button to get into the BIOS. Confirmed that it was now on v319. Shut down the device again.
Repeated step 2 to put in my new SSD. Did Cloud Recovery, which worked this time. Booted into Windows, which was a bone-stock version without all the drivers the ROG Ally needs, but because of Cloud Recovery was automated to install what it needed. Let it sit and do its thing.
Once done, I was finally able to boot into Windows. Had to do the OOBE initial setup stuff again. Once logged in, went straight to MyASUS and updated all the things again.
Was it worth the time and effort for someone who just wants to jump in? If you're not upgrading the SSD, absolutely, it's only a couple of reboots at best. If you are upgrading and you have little patience for these things, then no. But if you're like me, then these things are fun for you.
I still haven't done a Windows Update but that can be done at a future date. For now I'm busy playing lmao