I've only played one session of 3.5; I don't believe any of the PCs or NPCs in that game had spell focus. Since I play a lot of RPGA living campaigns, I'll be playing a lot of 3.5 in the future though. (Despite my opinion, that it is, over all, an inferior rule-set to the 3.0 rules).
However, I think that the contention that you have to have played with a particular rule in order to know how it will work is misplaced.
In 3.0, for instance, I played a Sor 6/Candle Caster 4/Elemental Savant 4 without spell focus. I didn't need to play him with spell focus to know that spell focus would not be a good choice for that character. Similarly, when I played a Wiz 10/Templar 1/Sacred Exorcist 1, I didn't need to play him with spell focus to know that it wasn't a really good choice for the character. (And I didn't need to play him without the Templar level to know that martial weapon: longsword, weapon focus: Longsword, and the templar level were suboptimal choices for a full-time spellcaster). Similarly, when I play my Living Arcanis clr 5 cohort, I've never tried her without spell focus, but I know that spell focus:enchantment was a good choice, given the style I play her with. And, for my Living Greyhawk Clr 7, not having spell focus is a good choice for the way I play him (having only cast two or three spells with saves in his career).
I've also had to give some thought to how the 3.5 changes will effect all my living campaign characters. It seems pretty clear that the Arcanis cohort won't be able to use the same tactics (since one of her favored spells is removed from her spell list and the other two have been dramatically nerfed--in fact, it's probably better for her to have a
lower DC for her Calm Emotions spell now that a threat or attack on any affected character breaks the spell for all of them; in that case, a 50% success rate that allows the party to fight the villains in two encounters of half the difficulty is better than a 60-70% success rate that allows the party to fight a few of them and then a whole bunch). I don't need to play her under the new rules to know that spell focus is no longer a good choice. (Just like I don't need to play a 10 strength human fighter with weapon specialization: small dagger to know that it's a bad idea and I don't need to play a half-orc Sor/Wiz to know that he's a "concept character" who will be much weaker than more optimized characters of the same level).
Also, playing with a rule doesn't guarantee that you will know whether or not it's balanced. Using the Living Campaigns as an example again, it seems to me that their Tralian hammer (exotic 2d8 /x4 crit weapon) is balanced in play compared to greatswords, spiked chains, rapiers, and longswords. But that's only because magical PH weapons abound and there aren't even any masterwork tralian hammers to be found. Similarly, because of the way the campaign tends to create encounters (lots of class-leveled humanoid opponents) sleep is a viable spell even for 6th level characters. And the domain that lets you turn undead as if you were three levels higher doesn't seem horribly unbalanced (there don't seem to be many undead). The same is not true in a more monster-heavy environment. Spell Focus, for instance will seem far more useful at +1 in a humanoid centric campaign that features moderate to large sized groups of foes than in a campaign where 60-75% of battles are against monsters and generally features single foes or small groups. (Enchantment specialists will enjoy a similar apparent power boost). And if the campaign is low-magic or cash-poor (preventing cloaks and vests of resistance from being standard equipment for moderate level NPCs), it will seem even more effective relative to what I believe to be the assumed campaign (50-70% of battles against monsters, and an even split between single foe (CR=party level +0-3), small groups, and moderate to large groups). The +1 version of spell focus will also work much better in a rolled or high point buy environment than a 25-32 point buy environment and will work better in an environment with nonstandard races (that give bonusses to spellcasting attributes) than a core-rules only environment. (The reason for this is that it's far easier to justify the opportunity cost of casting a spell with a 40% chance of success (starting spellcasting stat 20 and spellcasting prodigy) than to justify the opportunity cost of casting a spell with a 20-25% chance of success (15 or 16 starting int, no spellcasting prodigy). Playtesting is very much relative to the campaign in which it is playtested. That you haven't encountered a problem in your game doesn't mean that it's a good rule.
It's also worth noting that some problems don't show up until mid or high levels or unless certain combinations are used. I had a 3.0 house rule that clerics spontaneously converted spells to their domain spells instead of to cures/inflicts and it worked just fine for a year and a half. It worked just fine for the War and Healing domain cleric. When I got a Travel and Healing domain cleric and he hit 5th-6th level, however, I discovered that the rule didn't really work very well and dropped it--the ability to give the whole party Fly without having to prepare it (wizard) or select it as your only spell known (sorceror) was rather unbalancing. The revised spell focus looks like a similar problem to me--it will primarily show itself in the weakness of suboptimal (starting int or cha <17) spellcasters starting around 8th level in campaigns that feature a fairly large number of tough single creature and small group monster encounters. In campaigns that favor humanoid encounters or rarely have single-creatures, it won't show up until later. It won't show up at all if your party lacks the kind of spellcaster who would have ever found Spell Focus a good choice.
The importance of statistics and more abstract analysis is that it allows one to predict the results of situations that haven't yet cropped up in play and understand situations that have.
Ankh-Morpork Guard said:
While I still don't agree that Spell Focus is useless, this is something we'll never end up agreeing on...so I have another question along the same lines.
To all of you against the SF change, have you actually PLAYED SF at +1? Or have you simply just house ruled it without even seeing how much of a difference it makes? Statistics can only tell you so much, and from my experience actually playing with it as a +1, I've seen no problem at all...