Oh please.... persistant shield... argh...
You may be happy to know that Persistent Spell is going to be in the Player's Guide to Faerun.... but now it's going to be +6 levels.
That should make it hard to abuse!
Anyway, we see a lot of maxing of Concentration in our group, for two reasons. First, we have a house rule: "if you begin your turn threatened, take a 5' step, and do anything that would provoke an AoO, you still provoke the AoO from those that threatened you before you took the 5' step." The in-game reasoning is that they're doing their action while they take the step, and the out-of-game reason is, whe hate how casters can step back and cast a spell, or archers take a 5' step back and loose a volley of arrows without any worries.
The other reason is, bad guys are smart enough to grapple spellcasters. Everyone knows that they can't cast in a grapple, so being able to hit that DC 20+spell level required for casting in a grapple is important (escaping the grapple with Dimension Door is popular).
One thing that helps, however, is we have psionics, and the item Third Eye of Concentration is very handy. In the PsiHB, it's listed as a +10 bonus for 2,000 gp, but we've repriced it using the 3.5 rules. Still, at 2500, a +5 bonus is *very* nice, and has become a much sought-after item.