OneNote’ ink to text is one of its most impressive feature, and although I don’t use it a lot, it was a welcome improvement when it was introduced to the App version last summer.
In addition to converting ink to text rather flawlessly, OneNote UWP manages to differentiate font sizes and colors, and keeps the portion of text highlighted.

Oddly, whereas handwritten text can be converted instantly, it takes some time to be searchable. Actually, you need to be online, and it may take no less than 5 minutes before you can search for your ink.
Also, converting twice give odd results sometimes :

What’s more of a concern, is that text inked in OneNote UWP can’t be “inked to text” in OneNote desktop. Nor is it searchable there…
The opposite is not true nevertheless, meaning any handwritten text in OneNote desktop is searchable in OneNote UWP :

This means that OneNote UWP’ ink format is not fully compatible with the desktop version… (or retro-compatible, since the desktop version is older).
One last detail : OneNote UWP highlights the first result in grey, and the subsequent in yellow :

Sometimes also, the search if shown differently (as a selection in a resizable box) :

As a conclusion, I would not dare to use the same wording than Microsoft, which says that “OneNote for Windows 10…dramatically improved ink-to-text option”, but it’s great to have this feature finally available in OneNote UWP.
And although it behaves distinctly in OneNote desktop / UWP, and is plagued with retro-compatibility issue, you may enjoy the reliability of ink to text with no hassle if you stick to one version !
Further reading : Free vs Paid OCR article from MakeUseOf
Nota 11/09/2018 : OneNote UWP can OCR handwritten documents, provided you scan them with Office Lens :


It can be tempting to scan documents with a real scanner (useful when you need to scan several pages, or if you want to get better quality scan), and send them to OneNote through the “Send to OneNote” printer : in this case though, OneNote won’t OCR handwritten text… See this Reddit thread that offers an explanation.
Nota 06/12/2018 : OneNote desktop can convert all handwritten text (“ink”) to text at once : right click anywhere on the note, and select “ink to text”. This option does not exist in OneNote UWP.
Nota 02/04/2019 : I just figured out why some search occurrences are highlighted in yellow, and others in grey in OneNote UWP, and how to make use of it : when there are several occurrences of a word in a page, you may move from one to the other, switching the scope to the current page (CTRL F, then ENTER), and then pressing ENTER for next occurrence / Shift ENTER (or CTRL ENTER) for the previous : current occurrence is highlighted in grey. Thanks to Abhinav2107 for the explanation !