Of course they give you an edge. Try keeping a paper trail on table players in the time alloted for response clicks/bets/etc.
Its mostly an edge when multi-tabling. I played at my parent's house for ~2 weeks over the holidays, and I 2-tabled 6-max. Because there were only 2 to pay attention to, I was taking detailed notes on player's limp/calling ranges, watching how they play draws, ect. Those notes were a far bigger edge than just knowing they're a 60/15 fish, which you pretty much notice when they sit down with $41.35 at $50NL and open limp the first 2 hands.
So yeah, I wouldn't play 4+ tables without a HUD. You just can't get reads on that many players, so you need a program to keep track of it for you. But even still, my win-rate (bb/100) playing 1-2 tables with no HUD is higher than playing 6-7 tables with a HUD. However, I make more hourly playing more tables, hence why I do it.