I don't own a smartphone. I consider there to be numerous issues with them:

They are unequal devices. Smartphones are unapologetically devices for consumption. In this regard they differ critically from PCs, because PCs are equal devices in the sense that the same device is used for creation and consumption. This means that anyone with a PC can create as well as consume, if they so wish. This cultural equality is diminished by an exodus to devices which can only really be used for consumption.

They are not real network clients. Smartphones have powerful CPUs and fast network connections, except that you aren't actually allowed to use these resources in any meaningful sense, because doing so consumes battery power, and people don't want the precious battery life of their phones drained unnecessarily.

So there's a massive amount of computer power and network connectivity that in practice you can't use. This leads to an even more unfortunate and ridiculous consequence: you can't implement many existing network protocols on a smartphone. Or at least, you can, but not without draining the battery; but in practice, this isn't done.

For example, a disproportionate number of IM (XMPP, etc.) clients for, say, Android, appear to rely on a central server operated by the software maker, with some proprietary protocol between the client and that server, rather than simply implementing the protocol directly. In other words, there appear to be enough issues with implementing such protocols on smartphones that it isn't done. This leads to the next issue:

They have led to massive centralization. Part of the “cloud” movement is probably driven by the fact that while smartphones have substantial computational resources, you can't actually use them because of battery life. So instead the computation is done in the cloud, creating a dependency on a centralized entity.

How many of these smartphone applications being sold would still work if their makers went bust? By comparison, there is much PC software no longer sold but which is still cherished and used.

They have ruined web design. But I should probably write a whole article on that. Suffice to say however that I am very, very tired of the epidemic of (often massive) position: fixed headers on websites nowadays.

There are no secure smartphones. See this article.

They are devices of unclear alignment, or of clear malevolence. We can of course first rule out all iOS devices. This leaves Android. Supposedly, with Android you are free to install software from arbitrary sources and replace the OS. Except that these capabilities are all too often restricted by device manufacturers or carriers.

Except that if you look closely this doesn't quite add up. With Android devices there is a distinction between “rooted” and “unrooted” devices, which sounds suspiciously similar to “jailbroken” and “unjailbroken”. With a PC, I don't have to perform some arcane operation to actually have control of the device. Moreover, it seems to be common to discriminate against people who have the gall to “root” their device, or to disable some functionality of the device if such “rooting” is performed.

I believe there are even online banking applications which reserve the right, in their terms, to detect if a device is “rooted” and refuse to operate on them. In other words, discrimination against people who excercise control over their devices is common, and even sandboxed applications are permitted to detect this.

There is thus a prevailing expectation that people will not excercise control over their device, to the point where those who do are in a sufficient minority to be discriminated against, and have the functionality of their devices reduced for doing so. I suppose the PC equivalent would be a PC where, if you ever ran “sudo”, certain functionality would be permanently disabled and many applications would refuse to run forever after.