D&D 5E - Using Spell Point Variant Rule?

I was reading about the variant option of using Spell Points in the DMG (p. 288 I think...). I am thinking about suggesting it to our table and am curious if anyone here is using (or used and abandoned) the idea of spell points or their own version? If so, how did it work for your table?

I like the idea and don't mind the added complexity, but I do have some balance concerns:

At 20th-level with 133 points a character could have 19 5th-level slots, which seems really powerful.
As early as at 9th-level, a character could have 8 5th-level slots (with a point left over).
Even with Eldritch Invocations, the two 5th-level slots a warlock gets at the same level seem very underpowered by comparison.

So, is anyone using spell points? What issues (if any) have you come across?