Most Helpful Guy
Its a good sign for a second date, almost exactly as these other guys have been saying, but I wouldn't feel right unless I added in one tiny detail that is missing.
Here is how I react to differing quality dates:
Bad date: Don't text her, and avoid leading her on into thinking I'm interested.
Good date: Text her that night and try to give the impression I'd like to go again.
Mixed-Opinion Date: Text her that night and try to give the impression I'd like to go again. THEN, sleep on the matter and sort out whether any of the things that gave me a mixed opinion are deal-breakers, or whether she deserves a second date.
I bring up this third scenario, because if I'm not 100% sure how I feel about a girl when the night ends, I usually can't immediately determine whether its a good idea to give her a second date or not, but I'd rather leave the door open until I've had a chance to process what happened on the first date.
That being said, getting a text after a date should be seen as a VERY good sign you'll be asked on a second date.