No experience personally, but it's a high-velocity cartridge (93gr bullet at 1,200 fps) that was originally developed for the original DWM Pistole Parabellum, aka Luger pistol. It's also known as the .30 Luger. If you're astute, you may notice that the English and metric caliber designations are inconsistent with one another; interestingly, it fires neither a true .30-caliber (7.62mm, 0.308") nor a true .32-caliber (7.65mm, 0.312") bullet- it's actually 0.309" or 7.63mm caliber. It's one of only a handful of bottleneck pistol cartidges in common use, along with .357Sig, 7.63 Mauser, and 7.62x25 Tokarev.
The round has a reputation for gilt-edged accuracy, but also for a lack of effectiveness for SD or police use; as with other high-velocity small-caliber rounds, its greatest strength is that it penetrates like crazy, but this is also its greatest weakness, as it tends to create straight-through non-lethal wounds.
DWM was a German company, but the round's perceived lack of lethality prompted the German army to reject the pistol and call for something more potent. This led Georg Luger to shorten the cartridge case slightly and neck it up for a 9mm bullet, thus creating the ubiquitous 9mm Luger.
Despite the Germans' adoption of the 9mm version, the Swiss military and several other European forces continued to use the original 7.65 round, and it was also used for a large number of Luger pistols produced during the Weimar Republic era when the production of commercial 9mm pistols was strictly limited by the Treaty of Versailles. (The Nazis would later unilaterally renounce the treaty and restart full-scale production of the 9mm version, along with all sorts of other prohibited weaponry, but I digress.)
In recent years, the round's main reason for existence- besides use in original Luger pistols- is for civilian use in a few Western European countries that banned the commercial sale of pistols in so-called "military" calibers, IIRC notably Italy; 7.65 Parabellum was supposedly excluded from the "military" list for some obscure reason. Since the 9mm Luger round was originally designed to work in a pre-existing 7.65mm pistol, changing calibers the other way is generally quite easy- most 9mm pistols will function in 7.65mm with only a barrel swap, often using the 9mm recoil spring and magazines. Consequently, many older 9mm pistols were also available in 7.65mm for European sale, but these were seldom sold in the USA in significant numbers, making them sought-after collector's items in some cases.
Both Winchester and Remington have historically loaded the round, but AFAIK Fiocchi is the only company that consistently offers commercial ammunition in this caliber today.
