I've shot other folk's 15-22 with vertical foregrips and have yet to see what good they are on this particular firearm. They force the non-shooting hand into a very unnatural position. The concept was originally created for the M4 to aid in controllability in burst fire in combat situations - a situation that obviously doesn't exist with our rifles.
An angled foregrip, like the MagPul AFG and AFG2, used to help maintain hand position on the quad rail or other fore end in another matter, IMHO. When my son was in Bagdhad, he quickly ditched the issued vertical for an AFG2 I sent him.
But then, as I have said on other matters - to each his own weirdness.