These models have nearly double the contrast of both HP models (1000-1200:1 vs <700:1)=much better black levels. Screen uniformity varies but most have reported only small amounts of bleeding, if any. Not sure about tinting but I'm sure we would have heard about it like with the older IPS panels.
Yeah hopefully most of the major issues will have been revealed by now. I did not find out about the broken scaler on the ZR24w until after I purchased it and the PRAD and TFTcentral reviews made no mention of tinting issues on the LP2475w and U2410 at all
I received replies from various ebay sellers regarding the serial numbers, all of them responded that they couldn't guarantee anything regarding the serial numbers, so that's that. If the letter is indeed by month of manufacture I think we're all SOL if we want monitors with the higher refresh rate.
Without the refresh rate bonus I think the Shimian might be a better choice compared to the Catleap. The stands on these aren't that great and it looks like the Shimian's stand can be removed without disassembling the monitor. The price has also come down to match the Catleap.