We had a Brian Leonard version of this kind of player, didn't we?

If the Rams pick him as the #2 RB...I'm not that interested in giving up anything before the 6th round.  Unga looked pretty shifty for a big man in the Vids that I saw. But Unga is a pounder w/wiggle...not the speed & change-of-pace RB the Rams need. imho
He's a slow/average HB...but has the potential to be a very good FB....a guy who can catch out of the backfield and make a guy miss.  He is good for short yardage too...although they said he has some injury issues.

HOWEVER,

as it currently stands, the Rams current FB, Mike Karney, is paid an exorbitant salary(3 mil per yr to block and drop flair passes.)  If the Rams intentions are to cut Karney, and make Unga the new FB - essentially the Rams' version of the Eagles' Leonard Weaver,
....then, I'm all for it and would be willing to give a 4th, at most...but not a 3rd!

(remember the Eagles signed Weaver last year and he went to the Pro-Bowl - IIRC)...