One problem with Crouton is that you're reliant on Google for the kernel and drivers. When Google decides to stop tracking upstream, you're on your own.
For example, I found that I couldn't run XBMC on an older ChromeOS device without building my own kernel and forward porting Google's changes, which I failed to do. If I decide to buy a Linux laptop, I'd get a non-ChromeOS device.
Yup, that's true. I wouldn't go that route for media or HTPC type use.
It hasn't been a problem for me, for development use, as kernel dependencies aren't common in your typical stable of editor/compiler/interpreter/IDE/etc... The only real limitations I've hit for development are when you want to run local tests that require a container or VM system, where you do start worrying about kernel and drivers. But that wouldn't be terribly practical anyway, since the hardware (other than the pixel) is just too low-end to handle that kind of use well, in general.
Most (all?) chromebooks also support unlocking the bootloader which would allow you to install a stock linux distro running directly on the hardware, but you're right...at that point you lose all the benefits of chromeos, and might as well look at low-end pc laptops instead.
For example, I found that I couldn't run XBMC on an older ChromeOS device without building my own kernel and forward porting Google's changes, which I failed to do. If I decide to buy a Linux laptop, I'd get a non-ChromeOS device.