Oddly enough, I just got a Discover CLI from $2300 to $3500.
I hesitated since I recently hit the button a couple weeks ago, but was denied because of too much recent activity on my report (not sure what that meant exactly).
Discover doesn't seem to penalize for asking, so I figured ... why not?
I know it's not a huge limit for some, but this is the first time in my life my credit's been good and I've been very responsible about all my finances. It's the highest non-store limit I have right now. It feels nice to see the results of being responsible come to fruition.
It's actually pretty useful, since almost all my spending is going on this card since I'm in year one and getting the double-cash back next February.