Yea, I've had the misfortune of recently being introduced to the Segger J-Links (not the EDU version, the bigger ones).
The hardware seems alright, but their software is utter crap. At least the command-line stuff is, as I haven't tested their IDE integration..
Even if you disregard the softwares lack of documentation, idiotic arguments to the commands (which the debugger could have figured out itself), and other idiosyncrasies, there's very, very little value-add to a JLink compared to a $20 ST-Link, or even a $2 clone of a ST-Link.
Some people get hung up on Seggers "RTT" functionality, which on a powerpoint level looks great. Except, their software suck. As in, their logging-system _looses_ messages. Hint: The SEGGER_RTT.c files have no atomic functions or locking in place.
Right now, I can only find two good things to say about the Seggers (when they work).
First one: The time it takes to flash is slightly shorter, as they read out the flash, compare and then only writes the changed pages to flash.
Second: Their RTOS integration in the GDBserver is actually pretty convenient.
Oh, and in case you don't already know, the ST-Links (as all SWD DAPs) will work just fine with other vendors chips. You can use it to flash NXP, Nordic, Atmel, etc, etc. As long as they are Cortex-M with an SWD port (or JTAG for that matter), it'll work.
I might have mentioned ST-Link more than a few times here, but that's just because they're very easy to get a hold of. Any other adapter will do the job as well, such as (for example) a CMSIS-DAP.