Yes, I do use the seqs of both my Trinity and myTriton, and I must say I use them A LOT, especially when I´m starting a project, even some times finishing it.
(so can I cast two votes here?)
Thats the main reason, and not any other, why I like, buy, and play Korg keyboards since I have memory.
Its sequencers.
Deep, fast, easy to use.
Ok, ... I see some of you arguing at this point...
Are they upgradable, do we need more fuctions, added features, etc? yup!
But...Albeit far than being complete compared to the software standars nowdays, (no point to disscus here) Korg keyboards have THE BEST SEQUENCERS you can find in the Worstations market, and you can trust me ´cos I know well all others in almost any WS brand you can think of.
As Timo says, Trinity and especially Triton seqs are even good to control external gear if needed. I´ve done it a lot.
So, for me theres no other choice.
Korg is the brand I tend to use and its just because of its sequencers.
Final dot.

Regards.
D.