So one thing that really gets my goat is when I hear a guitar player going at it, soloing away, sounding great, and then he goes for a string stretch...
And doesn't QUITE make it.
It doesn't have to be fast, it doesn't have to be huge, it doesn't have to be the most amazing thing I've ever heard, because I get that everyone plays at a different level. But please - try to make it in tune!
String stretches offer a sound and emotion that just picking the strings normally can't touch, so it's definitely a skill worth working on. There are all kinds of different string stretches, quarter tone stretches, semitone stretches, one tone stretches, even one and a half tone stretches, but all of them require hitting the target note precisely; not just getting "close" and hoping that will cut it.
One way to work on making your string stretches in tune is to play along with a jam track. That way, your ear should be telling you that you need to keep stretching to make it sound good, or else stop stretching so far because you've overshot the target.
When you hear a stretch in the context of music, it really helps to develop your ear. Another way is to play the note you want to go to first, then train your ear to match it when you stretch.
The jam track method is more fun though, and gives you a feel for what it's like to play with all the trappings of a band... You get the rhythm section, bass guitar, some keyboards... All taken together, it really lets your solo shine through.
So be sure to work on those string stretches - and why not use some high quality jam tracks as a practice tool to help you get there?