does having two different brands of strings on one guitar make any difference at all to anything?
"Singin a song about a song that I wrote just the other day."
As long as they are the same guage you shouldnt notice any difference.
Fender Strat Roland Ready Edition
Martin D-16GT Acoustic
Fender Cyber Twin Amp
Marshall G50R CD Amp
My Myspace Music
I say always go with all DR's!!! Purple box is the 9 guage.

If u restring one string than go ahead and do the rest
depending on the packaging some strings have a wayyy different feel from other brands. D'Addarios for example have a less "sticky" feel than say that of GHS or Ernie Ball. guage is the real most noticeable diff. thought.
To me, D'adds and Ernie Balls are totally different even though they're at the same gauge. I prefer Ernie Balls, easier everything, pinch harmonics, my fingers doesnt get stuck, etc.

Of course, to some it may differ, its total preference, try a whole bunch and set your strings/gauge of choice.
"Play with your ears" - Yngwie Malmsteen, Paul Gilbert
Thats what she said...