Hi Eric,
And thanx for your comments,

1) That part was never designed for use with the 8051.
- Well it unexpectedly happenned to match it quite usefully.
Try "matching it quite usefully" with anything but a slow 12 clocker.
* Affirmative.

2) They were actually for the 8086 -so not even designed for an 8-bit processor!
- As far as mode 0 is concerned, 8255 is simply great for 8 bit operations.
Yes, indeed, it works fine as an 8 bit latch, but why not use an 8 bit latch instead
* When it comes to using three latches -not one- placed on the last three address locations 0xfffd to oxffff with the rest of the memory space allocated to say 28F512 without any address "aliases" for the three wise latches, the needed decoder does not look very friendly, you know..., the need for including A1 in the decoder and the proable extra gates needed to do that ... all the stuff does not yield to an elegant design, on the other hand, all the circuitry needed to provide the /CS for an 8255 placed on 0xfffc..0xffff is a 74hc30 plus one single NOR gate. If you have time, design the decoder circuit for yourself, maybe you can present a better decoder who knows.

3) made to match the x86 uCs and a lousy match for the '51
- The fact that it was made for x86 is not a reasonable argument alone.
OK, but how about "it is not made for the '51 as the WSI chips are.
* I'm afraid I shamefully don't know what on earth WSI is. I really don't. What does it look like? I ain't eaten one so far. ;) No offense, just 4 the fun of it.

4) It is obsolete, and it has been obsolete for very many years now!
- When no derivative with more I/O pins is available, PPI is still the best choice.
better than a couple of 74HC gates?, what is most likely to be obsoleted?
* It's a delicate decision.

5) 8255 was developed about three decades ago
(when the king of diamonds were still a jack)
- Wheel was invented some 3 millennia ago.
Yes, indeed, but the tire came later.

6) Using IE is akin to using 8255's in new designs.
- If only I could download the PLCC68 version of AT89C51RD2,
just like what I did with Mozilla FireFox to replace InternetExplorer Why whine "If only", I am sure that you can get 74HC chips. i would use a small CPLD instead, but appreciate that component availability may be a problem in some areas.

8255 might not be the best friend of 8051's great grand children, but let's not make it a
taboo word.
If it is not the best, why use it.
* In my sentence "might" was the operative word.

Have you had a look at the Philips IIC offerings such as the PCF8574/8575 which gives you
(4*) 8 '51 pins for two. These chips are "made for the '51", at least the ports have '51
characteristics.
* Sure, will do.