Wide guitars and clarity in the center.

I sometimes like to use something I guess I'd call parallel widening, send my guitars to an aux with S1 or something similar, increase the width something like 120%-150% and blend it in significantly lower than the main group, like -20 to -18 tops. Quite subtle, and doesn't work well on everything but sounds pretty cool when it does. The main issue I find with any kind of "widening" plug would be the phase issues that get introduced, as far as I'm aware the method they use to make things appear wider is actually by introducing phase irregularities between the L/R channels, and often this can introduce more problems to a mix as opposed to achieving the desired result, hence why I use it in a parallel fashion because I find those kinda plugs often remove all the punch and clarity from the centre when used directly as an insert vs. a send on an aux.

For my money, the best way to get good wideness is capturing a good tone from the outset, with tight playing, and hard panning the guitars with appropriate EQ choices to achieve the clarity and separation required to make them sound wider than other elements in the mix.
 
potshot: parrallel widening makes not really sense to me, if you want to minimize phase-issues. sure widening always fuck up the phase, but the widened signale will phase a lot more with the original signal, than by itself
 
Just a touch S1 goes along way and when used in extreme moderation I find it to sound quite awesome, it's a great plugin. Obviously there is something that happens to the tone but it can be a great trade off. 75 percent of the time I don't use S1 on guitars but it can sound good if dialled in correctly. I think the biggest contributing factor to making guitars sound really wide is making everything else not sound really wide. Kinda simple really ;)