Open Limping

Ok I was reading a post that recommended never to open limp. This really got me thinking as it is a part of my game that I feel like I need work on. What are everyone's thoughts on open limping?

If I have a hand that is playable UTG, such as JTs, QJs, does anyone recommend raising with these hands? I always was under the belief that these hands play much better in a multiway pot, so I should limp in a passive game hoping for 4 to 5 limpers behind me. I tend to throw them away UTG if the game is aggressive. A better example would be AJ offsuit, widely regarded as the cutoff "profitable" hand UTG. Is this an open limp or a raise? Or even a hand like 98s in MP if folded around to me.

I think I tend to play weaker in these scenarios as my preflop raise % is around 8%, where it should probably be around 9% or 10%. Any thoughts?