I have consumed many a PX in my life, maybe too many ... back to 1827 but in reality nothing older than 1910 and 1911 from the house of Mata. The 1927 Derek mentioned was when the solera began on that wine that he sold my buddy. Nicos prefers PX more than I do. I like it in small doses and imo, it lacks the complexity of truly great dessert wines like Port, Madeira, Moscatel de Setubal, Sauternes, German BA/TBA/Eiswein (Auslesen), Vin Santo, Banyuls, Quarts de Charme, Tokaji and many others that I prefer. Nicos would argue that I am crazy and that Pedro Ximénez is a stunningly intricate wine offering distinction and complexity.
I believe that the "myth" is that Pedro Ximénez was a soldier that brought the vines to Jerez in the mid-16th century from a country that I don't remember anymore. I know that Australia also uses it for dessert wines and it can be found in South America and even CA in small doses.
Pedro Ximénez and I first got familiar when I fell in love with some great Malaga bottlings ... the ancient gems of Andalusia (Spain) by a family named Mata. I happened on a stash of very old bottles and drank most. Earlier in this decade a descendent of that family contacted me from Spain and begged for any info I had on his family wine after reading my TNs from the mid-1990s that he found online. I happened to have some of the empty bottles around which were real art pieces and one that had never been opened. I told him I'd ship them all to him and did so. A while later, to return the gesture ... he sent me some great Spanish dessert wines he was involved in selling.
Pedro Ximénez is very thick and I joke that you can stand up a spoon in the drink. It is more viscous than almost any other wine type I can think of. It is like liquid raisins and mollasses with a backdrop of dates. The finish can be extraordinarily long, but unlike my friend Nicos, I find it to be simple, tasty and lacking the requisite acidity to be a true world class dessert wine. Like all Sherry, I find PX to be an acquired taste and not one that most people like the first time they try it. Then again, I personally can drink all Sherry except Fino ... and have never understood the pleasure that people derive from that dry style ... even though Sercial Madeira can be every bit as dry. I prefer Amontillado and Oloroso though, if I am choosing which Sherry to drink.
PX is something that I use to cook with quite often and Amontillado too. The former is great for searing scallops in and making a great reduction to pour cold over coffee ice cream. You can say you heard about that combo here first! It is a household fave when time permits. These are all made in true Solera style except for the real cheapies. However, it is not easy to spend a lot of money on any PX unless you are going after the 1910 Bodegas Toro Albala Don Pedro Ximénez Gran Riserva which is extraordinary. The 1971 that Glenn mentioned, is from this very fine producer and I have enjoyed the 1970/1971/1972 side-by-side and thought I was going to go into a diabetic shock.
The 1971 can usually be found very easily today and has been around on store shelves in good quantity since the late 1980s in the USA, when I first bought my first bottle.
The "1827" is actually a cheap but very tasty ($15-18) non-vintage PX that I used to recommend to friends ... made by Osborne (of Port fame too) in Jerez.
From my experience, although Bodegas Toro Albala is a very solid commercial producer, another fine producer of very inexpensive PX is Alvear. In fact, I believe that 1927 Alvear is what Nicos bought from Derek. Again, that is not the vintage but when the solera began.