I'd cast that summon over and over too. ^^ Never actually came in handy much, but still, was awesome to have Simba for a split second. :) he definitely kicked more tail in KH2 though, thankfully! ^^
Aye the actual animation that plays when you summond him was great, it's all part of the orignal KH's greatness. And he was the first summon you get, I used to summon him when heartless were low on HP so he would finish them off with Proud Roar xD.