Well I own a 7127, 8128, 8134,9129,9145, and they all cast, feel very similar to me. As I said I can cast these rods without a second thought. They are just an extensions of my body. Most people consider me a pretty good caster so I'm not a novice trying to learn how to cast.
I tend to use a lot of bottom hand but I find the 8152 doesn't really like that. It 'shocks' the rod. I find I need to use both top and bottom hand more evenly with the 8152. Maybe it's due to it's length and it's as simple as that.
The lines I've tried so far are Scandi style heads, Rio
, Mackenzie, Hardy etc in grain weights from 550grn - 650grn. I usually put a clear poly leader on these to make the heads a little longer, around 60' from rod tip to the fly. The poly leader also gives the line a little more grip on the anchor.
I have a Nextcast FF45 coming next week.
I think it is just me getting used to the rod as no one else seems to think this rod/design is any different from other Burkys. I'll figure it out.
I tried a Meiser briefly, 15' 7/8/9 Highlander classic and I used these same lines on it with no problem at all. The rod was quite a bit heavier than the Burky and didn't seem as sensitive to 'my' casting stroke, more forgiving. Don't know why but there you go.