Let me say that there's a reason all the advertising was done for first level stuff. Hint: it's not because "all games traditionally start at first level."
People get a handful of different abilities at first, and sufficient HP. From then on out, every ability you gain (less than 1/level) is really the same - damage that doesn't scale (and the damage doesn't scale well from level 1 abilities to level 30 abilities - you end up dealing, for instance, 5*Weapon + STR + magic bonus + feats. or 5d10 + Int + magic bonus + feats, for a DAILY power, when facing something with over a thousand HP), and one of the following:
*Daze/immobile/stun for a round (this is, sadly, the best of the bunch, as you can gang up with friends and Stunlock an enemy)
*Same as above, except save ends (so, it lasts for a round if you're lucky)
*Lasting damage (save ends. See: they always save, and no-one even cares about the piddly damage dealt)
*Slide them a couple of squares. They then walk right back as if nothing happened, maybe provoking (a basic attack, see: who cares?) on the way.
*You or a friend get a tiny bonus, and actually have to care about this bonus because it's what counts for good in this game: small bonuses instead of actual abilities
*You or a friend can spend a healing Surge
*You attack someone else for fuck-all damage
And that's it. And that's all you'll ever do. Everyone will only gain combat abilities, and spend them grinding away slowly at the massive HP of enemies (it starts off as ideal, then quickly becomes stupid. Before you know it, you're maxing out Intimidate just to force boodied enemies to surrender, and even then it will soon take too long just to bloody them). Skill challenges are completely retarded, disease DCs are in the "Yes, you will fail." range, rituals are completely stupid for a variety of reasons and still don't actually achieve much... all the game really has is combat, and that is boring and unimaginative.
Now, 3.5 + Tome material. Let's take some examples:
Fighters: can shatter Walls of Force, allow all damage dealt to count as "Ongoing" (so if they full attack a caster for 100 damage, then the caster needs to make a Concentration check with a DC over a hundred in order to cast on their next turn), an use a ranged touch attack as an immediate action to cause any action to automatically fail (spellcasting, attacks, movement...), can make two immediate actions per turn, can make a free 5' step on anyone else's turn and can make magic items with a craft check. They're masters of identifying monsters for bonuses, too.
Barbarians: become immune to mind-affecting effects when raging, gain relevant DR, add loads of damage to attacks, gain fast healing when they don't rage, and pick up various immunities and things. They're probably the most basic class still.
Knights: gain spell resistance, energy resistance and various immunities. They also grant Evasion to anyone standing next to them, can elect to take an attack for anyone next to them, and also can (as a Swift action) challenge a foe. If that foe fails to damage the knight by the beginning of the knight's next turn, then the knight adds insane amount of damage to all of their attacks against them for the round. Essentially, attacking the knight is a bit of a waste, because it takes a lot to kill them. NOT attacking the knight means you die. They also gain mounted combat abilities, and it is outright expected that after level 10 they are riding dragons instead of horses.
Samurai: cut through anti-magic fields and walls of force, have utterly deadly criticals, can make criticals happen all the time, get millions of AoOs (and an ability that lets them say "I'm taking all of my AoOs against you, right now, even though you didn't provoke), and can use their weapons to deflect spells away/back at the caster.
Rogues: it is outright assumed that rogues dual-wield acid flasks (ranged touch attack sneak attack, 3 attacks at first level and it grows from there), use magic devices to the full extent, and use "Bonus Feat" for the Rogue special ability to take feats they don't qualify for (as this is completely within the rules). This keeps them playing the same game as everyone else - and able to fight monsters. There are cheap-as-dirt wands of Gravestrike etc. to sneak attack golems, undead, plants and all the rest.
There are also some base classes for rogue-variants, such as the Jester, the Assassin and the Thief-Acrobat, all gaining cool abilities that are fun and useful.
Monks: can practically fly, are actually hard to hit, can actually hit their foes, gain SR, and can enter stances that provide relevant benefits such as "I hit you. Save or die.", "50% miss chance!", actual flight, teleportation, TK added to their attacks, ability tomake unarmed attacks at a distance, ability damage/drain on attacks, and "I hit you. Everyone except me within 30' takes 10d6 Sonic. No save. No, have the damage. Really, I insist."
The casters: mostly remain the same, except Clerics and Druids don't automatically know all splat-book spells (they can scribe them like Wizards, and gain ONE non-core spell per level for free), and Wildshape has been adjusted, as have certain spells, to not be plain stupid.
Monster characters are now actually playable, instead of a joke.
Instead of ignoring inherent problems in the game, it either fixes them, or makes them into features of the world.
Feats have been changed - you can do useful things with feats, especially the martial characters - stunning/dazing foes, reducing their movement, dealing Dex/Con damage, being taken along for free when people teleport near you (you choose to, it's not automatic), being able to ignore magical bonuses to AC, blindsense and two-weapon fighting that doesn't make us cry.
Think of it as "D&D 3.5 - you still know the basic rules! - except it's balanced so that when a CR X monster rocks up, everyone of level X can actually meaningfully contribute to the battle, and is also almost guaranteed to have something to do when the battle ends."
Now, if the Schuztaffel rocked up and said "Play 4E or Pathfinder, or I shoot you!" then I'd pick Pathfinder. I'd make sure to play on Easy mode by playing a caster, but at least I wouldn't be playing 4E. However, as it is, I'll bully/beg DMs into running Tome games for me, and it will remain the superior option, and is likely to be the best thing until either TGD completes "The New Edition" or we at Elliquiy complete the game we're working on, in which case one of those two will likely be the best.