Good guitars for the money. Great modding platforms, but with some caveats.
My samplesize was not huge, but I had a Classic Vibe Esquire. Fantastic guitar for what I paid for it. I modded it hard. The one thing that I didn't love was the neck was super sensitive to temperature changes, so it needed constant adjustment. No biggie, tho. Truss rod worked fine.
The other thing was the frets weren't top-quality material. Granted, I do play pretty aggressively and like low action, but mine were showing signs of wear even at early stages when I had it. Much faster than the other guitars I had at the time, anyways. Probably not a short-term worry, but if you're heavy handed, bend a lot, and/or is you main guitar and play it a lot, might need fret jobs and possibly a refret more frequently than something nicer. I think that's something that I haven't seen mentioned a lot regarding Squiers... or lower-end guitars in general.
That being said, I still want another Squier at some point kind of as a beater guitar, or just as something different from my Les Pauls.