I wanted to post a bit more regarding the "unlimited spell knowledge" point, because it's one that comes up so often, and appears to me, to be so erroneous.
I DO think this is a huge issue for Clerics and Druids in 3.5 and I usually, when DMing, houserule how many source books one can draw from. My two favorite houserules are "phb and any ONE other book; not the spell compendium" or "phb and any [light] spell from any book" for example, for a priest of the sun god. But I digress.
Let's talk about the limitations that are in place for wizards that people often gloss over.
Checking out this:
Arcane Spells :: d20srd.org
Indicates that a wizard DOES have to make a check to learn a spell.
No matter what the spell’s source, the wizard must first decipher the magical writing (see
Arcane Magical Writings, above). Next, she must spend a day studying the spell. At the end of the day, she must make a
Spellcraft check (DC 15 + spell’s level).
<snip irrelevant stuff>
If the check fails, the wizard cannot understand or copy the spell. She cannot attempt to learn or copy that spell again until she gains another rank in
Spellcraft.
So each spell takes 24 hours for a
chance to learn it. Success is not assured.
More importantly, here are the costs for spell aquisition:
In most cases, wizards charge a fee for the privilege of copying spells from their spellbooks. This fee is usually equal to the spell’s level × 50 gp.
and
A spell takes up one page of the spellbook per spell level. Even a 0-level spell (cantrip) takes one page. A spellbook has one hundred pages.
Materials for writing the spell cost 100 gp per page.
There is also the trivial cost of the blank spellbook, which has 100 pages, costs 15 gold, and weighs 3 lbs (too many spellbooks could easily encumber a low str wizard). But, as I said, that's trivial compared to the other costs.
I'm not clear on whether a wizard who failed to learn a spell would have to pay the copying fee of the "cost to learn". In my games, the wizard only pays upon successful copying of the spell. I could see an argument for the wizard to have to pay every time they tried to learn, however. After all, they are spending 24 hours with someone else's spellbook, and it's hardly that person's fault the wizard attempting to copy it doesn't have enough skill with spellcraft.
So there's the chance of the mean sourcebook wizard who charges every time, and there's even the chance of the supernice sourcebook wizard who never charges. Even in that case (which isn't really RAW and starts getting into monty haul territory) the wizard is only being saved a third the cost of the spell (2/3rds of the cost are actually writing it in his spellbook).
If we do have the mean sourcebook wizard, that means paying to fail on occasion. A lvl 1 wizard maxed in spellcraft, with an ability score of 18 has a spellcraft score of 8. Since the dc for lvl 1 spells is 16 (15 +1), the wizard will fail on a roll of 7 or below. This gets significantly better as the wizard levels, as at lvl 3 his spellcraft could be 10 (2 better from ranks), but the dc only goes up 1 for the increased spell level. Hence, the wizard fails on a 6 for lvl 2 spells and a 5 for lvl 1. Barring other improvements to spellcraft beyond ranks, the wizard has a 0 percent chance of failure for any spell starting at lvl 16. However, this ignores intelligence boosts from items and from the boost every four levels. In any case, a wizard starts his career failing approximately 1/3 of the time, which would be a hefty blow to the coin purse of a low level adventurer. Even if not charged for failure, it means that most low level wizards will have a difficult time learning every spell they feel like.
But for the purposes of the following, let's forget all about spellcraft DCs, and assume the wizard only ever pays for spells he learns (never paying for spells he fails to learn).
Basic fighter items, their cost in gold, and a wizard spell cost comparison):
masterwork chain mail 300 (2 level 1 spells)
masterwork longsword 315 (approx 2 lvl 1 spells)
+1 chain mail 1,300 (approx 3 lvl 3 spells)
+1 full plate 2,650 (approx 6 lvl 3 spells)
+1 longsword 2,315 (approx 5 lvl 3 spells)
The point is, that wizards DO have limitations, but too often (especially in message board conversations) those limitations are ignored.
Just for fun, I thought it's be interesting to add up the cost of all the sorceror/wizard spells in the SRD.
The total sum for all spells in the SRD (paying for every one) is 248,825 gold.
While I was at it, I added up the total spellbook pages that'd take: 1,662 pages. That's 17 spellbooks, for the piddly cost of 255 gold, and the not so piddly weight (for most wizards) of 51 lbs to lug around.
I hadn't done the math yet, but a +5 vorpal sword is 200,000 gold plus the cost of the masterwork sword (about 300 gold, give or take, depending on which sword).
So giving a wizard access to any spell in the SRD or PHB is like giving a fighter a free +5 vorpal sword along with another 48,000 gold.