When I started musing around VST plugins I looked for host which would suit my needs. I needed something free that would be usable for live playing or improvisations (as I can't read notes). Fortunately it was time when the Element was just open sourced and it definitely became my home DAW. It's very fast (even on slow machines), has intuitive interface and it's developer is very responsive on Github.
However - it's not built for conventional scenarios. It lacks timeline and all the recording (and sound editing) functions. I actually ended implementing my own four-track recorder VST, but this actually fits my workflow.
So if you are looking for conventional DAW for recording, this is not for you. But if you are looking for something fast for synth improvisations, sounds effect rack or for some modular environment this is your tool.
I was wondering if there was a freeware modular synth. I discovered this gem and was surprised that it even has a polyphony.
It's very well-advised concept and it has very good balance between simplicity and flexibility. Once you get idea about difference of master modules and voice modules (and common section), you are able to create simple polyphonic patches. And there is a lot of patches to steal ideas from.
Definitely recommended, only thing you can loose is your time playing with it.