The Shining Spears is a great multi-purpose unit - they really are among our most versatile units. However, that's also their problem; Eldar are specialists.
Reapers are better at shooting, and Scorpions are better at CC. Shining Spears land somewhere in the middle - capable of doing both rather well, but not splendidly.
You don't want to use them as a shooting platform; their short range puts them in great peril and their weapons aren't powerful enough to make it worth the risk. The idea is to use them for their charge, as you may already have figured out. A decent shooting attack followed by a powerful charge. Make no mistake - their charge is devastating to almost any target. However, I often find that I'm never in range to use the lances to shoot. They have such a short range that it's just not gonna happen very often. I find myself forced to use the catapults more often than not.
Then there is the problem of weak assault rules in 7th ed - any dedicated CC unit worth taking requires some form of special rule that allows it an easier charge. Scorpions, for instance, have Fleet. The complete randomness of the current rules means you end up not even being able to charge half the times, which is disastrous for CC units. That's the rules that are lackluster, however, not the Spears themselves.
All that being said - personally, I love them! I use them regularly with decent results, mostly due to their versatility. It is also a great unit to put an Autarch with if you're running with one. They do work fine without one, and it's a risk putting an IC with them as it makes your opponent more likely to shoot at them (and they aren't tanky at all), but if you have an Autarch with a lance or another powerful weapon leading them they will manage to dish out the necessary damage on the charge (which is what they're all about - they are weak in subsequent rounds of assault) quite a while longer. This is because you can afford to lose members of the unit. Basically - as long as your Exarch and Autarch are alive, the unit is deadly.
In other words, without the Autarch the unit could potentially have better longevity, whereas they will remain viable longer with one. At least that's my experience.
Since 7th ed they are also worth their cost, which has seen a steady reduction since 4th ed (where they were hugely overpriced).
I suggest you try them out, but keep in mind that their ability to charge is restricted by the meta.
I would recommend that you don't trust them blindly to make it into assault, unfortunately.
If your strategy revolves around charging something specific with a CC unit - take another, more reliable CC unit. Scorpions are my favourite for killing things that aren't too resilient. With a clawed Exarch there are few things they can't kill. If you are going to attack something sturdier, the Wraithblades are good, although they, too, may have a hard time getting in there.
You should always try to charge something, and remember that without the charge they are crap in CC. Don't get yourself charged! Use the speed of the bikes to make sure you're the one doing the charging, and don't charge units that you can't obliterate in the turn you charge, or, preferably, in your opponents following turn.
