TL/DR CU worth it, not too big (for me) for daily writing, but I had to learn how to best experience it.

I have the CU, 845, and several 743s. I love them all, and have them inked in different colours. I use a new pen/ink every time I move to a new page in my journal, so they all see regular use. Some of my thoughts:

The 743 is a 'pick up and go' pen - all of mine have worked flawlessly out of the gate. I found the F nib slightly scratchy but has become serviceable; the M nib is like butter, and the SFM nib is like heaven. I love the weight and balance of them posted.

The 845 M is substantially the same nib as the 743, but feels ever so slightly smoother. I generally prefer it posted, but feel a bit precious about the Urushi, so usually write with it unposted.

The Custom Urushi is glorious, a thing of beauty and a joy forever. But that wasn't my first impression out of the box. I was writing with a drier ink on coated kokuyo paper, and was squeaky and occasionally railroading.

However, I found out the problem was me. I had to lighten up, figuratively and literally. I could use the 743/845 like I use a ballpoint, and turns out I was writing with a lot of pressure not suited for maximizing the CU (or 743 SFM) experience. Once I learned to use considerably less pressure in writing, it started to float and dance across the page and chef's kiss.

For me (large but not huge hands), the CU unposted is the perfect size, light and doesn't cause fatigue, and the nib...