I have, use, and like my iPad. I have had one in some form or another since the second gen, and I use it every day for something. I also have a Windows computer.
Using my iPad for music is something I've tried several times over the years, but so far it has not really stuck for me outside of some edge cases (e.g. some unique musical toy apps, hooking it up to a MIDI keyboard and using it as synth module, having some fun with Korg Gadget).
At the same time, I can't imagine playing like 3D action games on it without a controller, but there are kids and teens who grew up with touch interfaces and do that all the time. I can't imagine using one as a main office computer either, but I know people of all ages who have basically ditched normal computers and use iPads this way, connecting a keyboard and sometimes mouse in when they need to work on documents.
If someone has an iPad or iPhone and just wants to record some tracks, it's kind of hard to recommend they buy a PC or Mac just to do that when an audio interface plugged into their iDevice will get them very far. For serious mixing and all that, I think it's easier and better to go a "big computer", but for a lot of situations it might be more down to that generational disconnect just like with the games.
There's a reason that Fender's current page for Fender Studio doesn't even show a desktop / laptop screenshot until the very bottom of the page.
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Re: this vs GarageBand on iOS, I think there is an interesting difference. If I make a song in GarageBand for iOS, there is always the option to later graduate to Logic Pro and take my projects with me. If I don't want to use the subscription-based version of Logic on iOS or do want to go to a big computer for more intensive mixing and production, that basically locks me into getting a Mac, which I may not want to get, may not be able to afford, or I might already have another a non-Mac computer I can use.
Fender Studio on the other hand allows project export in the open DAWProject file format, meaning I could upgrade not only to Studio One, but also to Cubase, Bitwig, and possibly others (I'm not sure who all supports it yet). Not to mention simply transferring my project from Fender Studio on iOS to Fender Studio on Windows, Mac, or Linux if I'm fine with the feature set.