I have used the X-Rite i1 first version with DisplayCAL and also the ColorHug on several monitors and laptop screens for a few years. The i1 had a cheaper version and a more expensive one that only differed in the software supplied (for Mac and Windows), but dispcalGUI and Argyll CMS would supply the tools of the Pro version of the software with the lower priced i1 package.
Both tools worked well and really improved some monitors and all laptop screens. I've used an $1800 Eizo and now an ASUS ProArt 279 for the last several years. Those haven't needed as much profile adjustment, and the ASUS has a hardware switch for profile toggles that includes sRGB and Adobe RGB with very tiny Delta E (<2). So I haven't felt the need to calibrate as much. (The hardware toggle is very handy when you're editing RAW in Adobe RGB and want to check output in sRGB.)
I can't find it now, but I believe I saw a reference stating that Richard Hughes is/was (?) involved in writing display drivers or something involving color management for Red Hat, i.e. he knows what he's doing.