Sorry folks, still recovering from a production party
Operaman, you working anywhere yet, and if so you mind me askin where? Currently out in Santa Fe for the summer myself. I work as a tech though, I have no real interest in being on stage, no offense intended of course
To each their own.
At any rate, as suggested, I have heard good things about Ubuntu Studio. ELive actually does a decent job as well by default, I have been meaning to load it on a virtual machine and build a realtime kernel for it, haven't gotten around to it yet though. The default does decently though, and if you don't need realtime performance it can be worth looking at.
There are a few others, musix, 64studio, etc. For the time being I think your best bet will be Ubuntu Studio though, it ships with most of the software you will want.
The catch I think will be your audio interface. The Focusrite saffire is supported by freebob(Now FFADO) but the mixer and DSP onboard are not. It will be a straight audio interface if I understand correctly. I can only help you set up freebob so much though as I don't use it myself.
That can be a loaded question.
First and foremost you will need JACK (The audio connection kit) for most pro audio software on Linux. Jack acts as a kind of patch bay for all of your software, as well as providing things like transport control and sync. It is a very good thing to have, and to launch it I recommend you also get a hold of QJackCtl, which is pretty well the standard control for it. Also FreeBob acts as a backend interface for Jack instead of Alsa, to my knowledge there is no ALSA driver for Jack yet, it means we will need to look into other options for ALSA software(Can get to that more later)
The first software I would recommend you look at is Ardour. (www.ardour.org
Ardour is a recording/non-destructive editor. You CAN use Tape tracks for destructive recording if it is easier for you, but in general it is build for non-destructive recording and does it very well. It does not YET have Midi, however that is being developed as we speak in fact as part of Google's Summer of Code, so hopefully will be in before long.
RoseGarden is one to look at for Midi really. It is a Midi Sequencer, and some people love it. It falls short in audio though, so I don't use it much myself.
Muse kinda provides a middle ground between the two, at this point I haven't used it in some time, the last time I used it it wasn't as good at audio as Ardour, and wasn't as good at Midi as RoseGarden.
All in one programs... Not so much. As I mentioned Ardour will be getting Midi, and Muse takes on Both midi and audio. That is as close as you will get on linux probably, nothing with built in softsynths etc. The reason is a LOT of Linux is based around modularity in audio with Jack. Example...
Suppose I want to record a softsynth like ZynAddSubFX... Assuming all hardware is up and running, and Jack is up and running. I would take my Midi Input and route it via Jack to ZynAddSubFX. I would then take the Audio output of that to Ardour. I would then take the audio output of Ardour, and route it to my interface audio output.
As I mentioned Jack acts as a large patchbay, and if you think of it like that it makes things much easier IMO. It also allows you to use all sorts of different tools in your tool chains.
I am afraid I am not as familiar with SoftSynths to be able to recommend any of these. As i mentioned above, ZynAddSubFX seems to be fairly popular so that is a possibiltiy I suppose.
Here are a few links to lists of software for you, the real problem with Linux is finding the software that does what you want, it is probably out there, but there is a LOT of choice out there(Part of the beauty of Linux at the same time).
First the always popular Wikipedia(Smaller list):http://en.wikipedia.org/wiki/Linux_audio_software
Next we have the Linux Audio Portal...http://portal.linuxaudio.org/
Specifically in this you might want to look at...http://apps.linuxaudio.org/
Which I believe has most of Dave's original list I believe on it, but just in case I believe it is still hosted here....http://sound.condorow.net/
As you can see there is a LOT of software out there. You will notice on the Linux Audio Portal a mailing list for Linux Audio Users, it can be a good place to get info, but always search the archives if you can first to see if someone else asked the same question.
So in short, I would recommend you try out Ubuntu Studio first and foremost, that will ship with most of the software you want I believe, and it is easy to install any new software you decide to try. Eventually you may decide you want more flexibility than what is offered by prebuilt binary distros, in which case Gentoo is your best bet, but many people find ones like Ubuntu Studio work well for them.