HIT is a bit of a confusing stat in World of Warcraft for a mage.

Spellpower is easy.  I can see the impact of spellpower every time I cast a spell...I see bigger overall damage numbers when the spell lands.  Crit is somewhat easy...enough crit and I can start to 'feel' that I'm getting more crits, which is rewarding.

So when I gear up for HIT at the expense of some of these other stats, it makes me feel weak, lame and gimp, with a bit of wimp mixed in.

If HIT gear doesn't appeal to you, there are two things you can do to convince yoruself of its value: start tracking your raids and examining WWS, and use RAWR.

WWS (wowwebstats.com) is a service where you can upload combat logs from a raid and it parses out the information for you.  You can compare yourself to other mages, and check fight-by-fight how your DPS looked.  You can drill down to the details of how many spells of which type you cast, etc.  And you can see what percentage of your spells were resisted or missed!  WWS can be a bit technical (and clunky) to use, but if your guild uses it, take advantage of it!  The thing that helped convince me of the value of HIT back in Burning Crusade was comparing my DPS to other mages.  There was one guy who was way ahead of the rest of us...even though we were casting similar number of the same spells.  AND we had higher spell damage gear!  But he was geared for HIT, and when we looked at the resist percentages in WWS, we noticed that he was landing a lot more of his spells.

RAWR is a program that you can download to help you understand gear choices.  It is generally considered an authority on how all the WoW stats work together.  It integrates with the armory, so you can upload your character, and start examining what pieces of gear would be an upgrade.  (And it integrates with wowhead, so you can easily click on an item to find out where to get it.

The trickiest part about RAWR is configuring it.  It is important to configure the options to closely represent the fights you want to model.  Remember, for raiding, trash mobs don't matter....trash mobs will go down even if you aren't going full out...it's the bosses that require the maximum effort from your character.  So you have to set things like fight length and what raid buffs you will have.  Some people get confused as to why RAWR might, for example, value INT gear so heavily...but if you have a default fight length of 5 minutes and your normal gear has you running out of mana, RAWR will calculate the best gear for you for that fight.  Even if it's gear with lower damage but higher INT, it will figure out if the lower damage over greater time will be better than higher damage but having to stop DPS to evocate, for example.

That being said...once RAWR is configured, it is AUTHORITATIVE.  It is programmed by very smart statistician/gamers, and is reviewed by people who, it seems, their only job is to figure out the statistics around World of Warcraft.   I have seen many people try to build a spreadsheet or do the math to figure out what spec is the best or what gear or what spell rotation, etc.  And they all fail to account for one factor or another.  RAWR gets it all, for the most part.

One of the cool tools of RAWR is an 'optimizer'.  It lets you select all the gear that is available to you (in your bank, from the Auction House, craftable, etc.).  You pick which pieces you want to choose between, for each slot.  You input the fight parameters, and you input your priorities (survival, DPS, overall, HIT, etc.), and it will compile the combination of available gear that does the best.  It's pretty cool.

AND you learn something about the value of HIT.  Generally speaking you want to HIT cap...BUT  you don't want to do it at the sacrifice of too much damage.  If, for example (these are not real values, though they may be close), HIT is worth 2 points for every 1 Spellpower point (until you are HIT capped), you will want to gear up HIT as much as possible...but you wouldn't trade out a piece of gear with 50 spellpower for a piece of gear with 20 HIT just to get you closer to cap.  You'd actually lose DPS by giving up too much SPow for the HIT.

So, how to answer the question, "Should I gear for HIT Cap?"  Yes and no.  Yes, as long as your overall DPS won't suffer.  After all, you want to DPS, right?  That's what it's all about!  Your DPS will generally increase by upping your HIT, but there are many factors to consider.  RAWR can help you consider all those factors and make the best balanced choice.