Olaf the Stout
Legend
No, it means he's really hard to grapple three times per day.
I know I can only speak for my game, but I haven't had a situation where the Conjurer has put himself in a position where he can be grappled 3 times in one day. He normally makes sure he is well protected by the front line.
And it is worse than "really hard to grapple". He can make a grapple automatically fail 3 times per day. According to the PHB2 errata all Immediate Magic effects are supernatural abilities. So the Conjurer doesn't even have to make a concentration check to succeed. It also means that activating the immediate magic doesn't give an AoO.
Not all attacks, not always, and, again, only three times per day.
I realise it isn't all attacks. However, if the conjurer gets charged or gets in to melee combat with an opponent he can choose to cause an attack to have a 100% miss chance.
If a player wanted a magic item that guaranteed his opponent's attack would miss him 3 times per day how much do you think it would cost? Do you really think that sort of ability is ok for a 1st level PC?
And in regards to it only being 3 times/day, how many times a day do Conjurers get in to melee combat? The Conjurer in my group is almost never in melee. If you are playing a Wizard and you are in melee a lot you should be worried.
In addition to causing an attack to miss, it also allows PC's to move away from opponents with 10ft reach without giving an AoO. You simply teleport away and then move normally.
Finally, it isn't actually 3 times/day that you can use the ability. It is a number of times equal to the PC's intelligence bonus. So for my player's PC it is 4 times/day and will increase to 5 times/day at 8th level (we use point buy and he sacrificed his other stats to get an 18 Int to begin with).
Olaf the Stout