I just switched over to it a couple months ago and it's great. My labs are unchanged. I see no reason to do IM anymore. Why use bigger needles than you have to, right?
I like to inject on the side of the abdomen, the "love handle" area since I have stubborn fat there. I pinch some fat, go straight in, perpendicular to the skin, all the way to the hub. I get zero pain, soreness or noticeable lumps there. Total breeze. If I inject closer to the belly button I get a slightly sore lump.
Sometimes I'll also just use insulin pins in the vastus lateralis where I don't carry any fat, so it's actually shallow IM. Works fine for me.
I use 28ga, .5cc, .5" syringes. I can push .5cc into either site with no issues. It's actually faster than using 25ga, 1", 3cc syringes.