I've done some serious surfing in the last week. FULL CLIP has one of these on his Albainian if I recall - ask him!5L
Yeah, I HAD one on my Albie but removed it after too many sleepless nights of worrying about 922r. It's basically impossible to make that rifle compliant as you can't change out the stock and handguard. So now it's in STOCK mode again, which is fine. I'll legally use the Tapco grip on another rifle. Anyhoo, I though it was a great add-on and offered better control for follow-up shots. The installation is easy but does require drilling your trigger group (as others have described), so you may want to buy a spare for this purpose.
This is what is USED to look like:

Of note in the FAQ in "Legal":
What’s the deal with “pistol grips”?
The 1989 Ban restricts “separate pistol grips”. The now defunct 1994 Assault Weapons Ban restricted a “pistol grip that protrudes conspicuously beneath the action of the weapon”. The 1994 language makes no mention that the pistol grip be “separate”. Therefore, it is generally accepted that for the purposes of the 1994 AWB, thumbhole and “Dragunov” stocks are considered as having a pistol grip. Whereas the 1989 language seems to require that the pistol grip be separate in order to count as a “restricted feature”. This reasoning seems to be supported by the fact that Russian made VEPR and other rifles are imported with thumbhole stocks.
However, it's not exactly clear what ATF considers a “separate pistol grip”. The grip on an AK rifle is completely separate in that it attaches to the receiver separately from the buttstock. On the other hand, the grip on a thumbhole or drag stock that is not considered “separate” is completely enclosed by and integrated into the stock. One wonders about the ATI Ultralight—does “separate” mean “not enclosed”. And as for pistol grips that bolt onto an existing stock, since there is clearly a separate piece attached to the stock with screws, one would think that ATF would consider these as “separate”.
Also see the explanation of thumbhole stocks and the 1994 AWB
Warning: This ambiguity means bolt-on pistol grips and certain aftermarket stocks should be treated with caution when considering the requirements of 922(r).