Conway Stewart was making some very nice pens, and then decided to go for the super expensive, limited edition pens like MB and others. But their quality control tanked, customer service wasn't good, and they couldn't pull it off. The pens often wouldn't write, and the Churchill lever filler had to be tweaked to get it to work. That doesn't sit well on a several hundred dollar pen.
The Italian celluloid (sorry Giovanni) has been awful. The glorious coral Visconti Voyager is crumbling. I've had some Omas LE pens come through the shop where blind caps rotted away. That shouldn't happen.
Wing Sung OTOH is making some very nice pens. I bought some of the Prera knockoff pens (3003), and they're every bit as good as the Prera at a small fraction of the price. Just for fun I bought the 626 Balance knock off. Its celluloid, threads are a little tight, but in general its well made. I expect to tweak the nib on most any pen I buy, and usually have to. But the 626 nib wrote very nicely without any intervention on my part. If the celluloid rots after a few years at $30 I might care, but I won't feel burned. But then again maybe they used celluloid acetate. Funny how Esterbrook did that, made their trim out of stainless, and their pens were inexpensive, but are still around and often in decent shape.