My experience is that it's so very frustrating and anxiety inducing!!
Im a FTM, 27 weeks with a high anterior placenta. I didn't feel a thing till over 22 weeks and even now, it's different every day.
I do feel her in some way everyday but it goes from regular, strong kicks all day one day to the gentlest of flutters the next. Some days I go hours without feeling a thing, some days it's only when I lie still on my side for an hour or it's just early morning/late at night with nothing inbetween, other days it's constant.
Several times I've nearly rang up concerned with lack of movement but she moves just in time!
My midwife said it's totally normal with an anterior placenta and that 24-28 weeks is the worst time as you've started feeling movement but there's no pattern yet. At this stage, baby still has lots of room to move around so the slightest change in position can make a big difference in what you can feel.
It's very stressful but I take some comfort in knowing that it's normal.
(Obviously as an add on to this....always trust your gut. If something doesn't seem right, ring up. Better to be safe than sorry)