oh... and what i'm doing for my next show is instead of stacking so many synths i'm midi learning on-off selectors for independent voices.  that way i can have 3 voices set to one on-off control and midi learn reverse on the other 3 voices.  click one button to flip the on offs and it's like having two programs loaded simultaneously in one synth. 

I know I'm a little late on this post, but I thought I would talk about my experience with this topic as it is something that I have slowly worked out many bugs in my attempt at making this work.  
Currently I have a pc rackmounted in a rolling rack case.  I use Sonar X1 as my host software, a m-audio Delta 44 for audio and a motu micro-lite as my midi interface.  I have numerous virtual synths in the arsenal including the Korg analog and digital legacy series, arturia V collection.  I use the Korg ms-20 controller, a 61 key m-audio controller and the Roland pk5 as a foot controller.

I play in a power trio similar to rush, tool, and the like.  my duties are bass and keys.  I have to be able to change sounds, trigger pre-recorded sounds, and sometimes just play keys.   I pretty much cover the gammit in dealing with the issues. 

Thanks for indulging on the background info, but now you know where I'm coming from with regards to this issue.

This is what I've learned in order of importance:

1)  Battery backup if you're running on a pc.  I use a rackmounted ups in my rack.  This saves your pc from spikes and the inevitable tripped breaker.  You can also play in stage power is out but FOH is still good. 

2)  Solid state hard drive as the boot drive.  This can take the abuse of road life much more than a spinning disk.  Plus it will improve boot time tremendously which can be huge for those 'you have 15 minutes to setup' gigs.

3) Make sure your controllers have midi out. If you use Cakewalk/Sonar you know that it will sometimes decide to re-order your synth's Id in the midi devices.  An absolute headache/show stopper.  Cakewalk has yet to address this and it seems they're not going to so....  Make sure your controllers are midi out so the order remains the same through your midi interface.  Otherwise you will go to play a sound on one controller and get a sound you did not expect.  Not cool.  I continue to have this issue with my ms-20 controller and it is going bye-bye because of that.  USB is too much trouble live.

4) Get a controller or controller that is versatile.  If you intend to anything more than just pull up a sound a play it then the versatility of your controller will be priceless.  I recently (within the year) upgraded my foot-pedals from the studiologic/fatar pedals to the Roland and I have freed myself from many headaches with regards to patch changing, triggering the interface, etc.  MMC control, knobs, sliders, assignable buttons.  All good things.

5) Try to get a 1/4 output for your audio.  this makes it much easier when dealing with direct boxes and the likes.  Plus it just gives the sound-person a much better feeling when you hand him/her a 1/4 regular cable for the directbox rather than a 3/8 or rca.  The latter two will get you a interesting look at best.

there are many other minor things I've learned while doing this, but those to me are absolutes.  I'm sure some will disagree and that's cool.  I just thought I would add my 2cents (or dollar based on the length of this post ;-)

good luck.

pj

Guys if you want to play out live we need to request a feature I've thought of taht could make all our lives easier. I've even put in a request over at sonarmods.com to see if those guys are interested in helping out. We can use next or previous marker and maybe make a snapshot at a marker create a new scene while playing live but I think it would really be cool if we could use a foot controller and have it switch the now time to any marker we want to go to then by setting up regions of time between markers of like 10 to 20 minutes we could play and never experience a scene shift till we called one up using a switch either a pad on a keyboard or foot switch like on a line 6 hd500, GR55 or even a behringer fcb1010. just switch projects to get more sounds and tweaks. What do you guys think of that idea?

I'm a guitarist / keyboardist and I have been looking for a solution to allow me to use ampsims live and get foot switching / patch switching functionality that would work and this the only way I can think of to make that happen in sonar.