QSPICE is a new and fast SPICE simulator written by Mike Engelhardt (author of LTspice). QSPICE was initially limited to beta testing in May, then expecting to become open beta testing in July.
Quick start gives a quick overview of the UI and other elements of the software. Below are few more videos on the features.
Gotta say that when Mike says modern UI, I'm not that impressed. Feels like us electrical guys always get some of the worst CAD/sim UI designs compared to mech, civil etc. With few exceptions like Altium which imo has a great modern UI.
Yeah, modern is a bit of a stretch, the GUI is only modern relative to LTSpice. The syntax suggestion when typing looks useful, and maybe the C++/Verilog blocks would expand the parametrization capabilities. Right now I kinda cycle between LTSpice, PSpice for TI, and QUCS, and the latter two are the most powerful.