(raises hand)
This is why I tend to prefer sorcerers over wizards and in Pathfinder oracles over clerics. I'm going to be using the same spells over and over anyway I might as well cast more per day and be able to spam a spell if I need to. In one of my games I'm playing a Life Oracle and am loving it. I get to play a "cleric" in every way in my usual mode with the freedom to cast as needed. Last game I was able to spam buff the party on Bull's Strength and Shield of Faith before a battle I'd never have been able to do as a cleric. I can still cast Bull Strength or Divine Favor on myself for combat and channel energy as a revelation for when I need/want to go into healbot mode. Finally I get to play a "cleric" how I always dreamed of playing one. The one level delay in spell progression is irrelevant to me. I'm sure there will be a combat where I wish had a spell I don't, but that's not going to happen often enough for me to worry about.
If "concentrating on a spell" for a round means more than just me sitting in the chair telling the DM "I maintain the spell", then it might not be so bad. If I get to make decisions and manipulate stuff that are effective through the use of this one spell, then I'm engaged. I'm contributing. I like that suggestion 'Dice gave.