Despite coming out like a 
I have to ask, since I don’t know:
1. Let’s say I have a crapload of hardware synths and I’m using Renoise to make songs using these very synths. How do one record all this? I guess you can’t just hit Render Song to Disk since it’s not Renoise that is actually producing the sound.
2. Is it possible to use both hardware synths and samples in Renoise and record both?
Thank you for helping a Renoiser out.
If you have connected your synths properly to your soundcard, the easiest thing is to use a line-in device on the same track you are triggering your midi notes from. Select the correct input on the line-in device and the sound should appear in the track. You also might want to try out different latency settings. When rendering song in realtime the line-in devices will be recorded too (new feature in the latest version of Renoise).
(Let’s hope for freeze of single tracks to be added as a feature in Renoise. That would improve workflow with hardware synths a lot.)
Let us also hope for “Plug-In Grabber” to get an update which allows for “external hardware grabbing” 
i still find myself whacking voxengo recorder on the master. not ideal, but hey it works. 2.7 does support realtime render though, so if you’ve got your midi all penciled in, you can hit that and render it all.
I actually do it more simple:
Renoise uses audio-out connected to a hw-mixer and sends midi to my synths.
Synths are connected to the same mixer.
Headphones for monitoring and the master-out from the mixer goes back into my computer.
This way I can monitor latency and mixing and play live stuff from my synths.
On my computer I use Audacity to record the audio-in stuff, so Renoise and Synths.
If you want to do mixing per channel after some recording, you could record each Renoise-midi-synthtrack with the in-device to a new Track in Renoise.
After that Mute the Midi-channels. If you change anything you can record the track again.
Use your Synths clean if you want to use Renoise-effects.