I think UncleSquirrel did a great job so I'll just tack on stuff from there
[D]Main likes from 4e:
- Greater numbers of HP, especially at 1st level - gives a higher-precision granularity for players to be able to be wounded without being killed.
- Ability score purchase system (pg. 17, Method 2).
- At-will cantrips.
- More stuff for fighter types to do in combat.
- The idea of per-encounter powers in general.
- The general attempt to lower the barrier to entry to new players (simpler character creation, etc). However, this ends up being the source for what I consider one of 4e's biggest weaknesses (its homogeneity).
- I *think* I like the pervasive "level / 2" and the "core mechanic", expression of "Attack vs. Defense" as DCs (e.g. "Charisma vs. Fortitude"). I think. Still debating that.
Main dislikes from 4e:
- Trying to make all classes equal by making them all alike.
- 1st level characters breathing acid and teleporting at will; I'm a low-magic-world kind of DM. In fact, 4e seems to have a general built-in assumption of a high-power, high-magic campaign setting; 3.5 and previous didn't seem to dictate such things as strongly, it seems to me.
- An over-emphasis on damage, rather than creativity and manipulation, in combat (e.g. non-combat Rituals).[/D]
The HP are both larger at 1st level to prevent easy death, and yet also consistent (which helps fairness) and smaller as PCs improve. This relates to the mechanics for healing surges and everyone being able to heal themselves. The intended mechanics for power usage in 3.5 suggested that, in later battles as resources includnig HP are consumed, PCs might not enter combat at full HP. 4E lowers the overall HP total slightly for the precident of expecting PCs to enter combat always at full HP. I think it's a smart move.
Yeah, point-buy rocks. I also find that adjusting point-buy totals is a great to change the power level of different NPCs or cohort to PC power ratios.
At-will Cantrips rock. When 3.5 came up with reserve feats, same thing. Weaker at-will power, rather than slapping the mage on the hand for casting too many magic missiles for the day.
The power moderation is great because power creep really was, IMO, the worst aspect of 3.5. Unilateralness is great; homogeneaity is not. As per a recent post of mine, I like how save work: a set per level boost, but also additional class bonuses. A retrofit to 3.5 might work like this.
I like the increased tempo and speed, even rounds seems pound-for-pound weaker. There should be some but not too many available choices. 3.5 seems to have too few choices at low level and too many choices at high level, with all the possible spell choices and item to buy or craft and using every standard and swift action possible. This also makes small bonuses more valuable over time, so looking for combat advantage or other positive circumstances in combat is more worthwhile.
I like the increased focus on drama and action points. PCs should be able to make fun, intriguing choices and eschalation builds tension, not save-or-die effects.
4th Ed feats just seem really pointless to me. Maybe it's a step in the right direction towards choices and not power creep, but it feels boring.
4thEd philosophies might be key in finding new solution for 3.5 epic problems. I mean, the 3.5 game brakes down around level 30 just like the 4E game, but that could be boosted a bit... 33, 35, maybe 36 or 37, not likely 40. There's just no way to powerscale everything still work at that point.
I like the distinct made between in-combat spells and effects versus out-of-combat effects. Healing, fireballs, and webs are not used the same as 1 hour/lvl buff spells, breathing underwater, even flying. I feel 3.5 is bloated with too many spells, but at least they are mostly in the same book (spell compendium).
You guys have probably noticed too that at-will, encounter, and daily powers fit well into the online, real-time RPG idea of cooldown times on powers (think WoW). I don't mean that in a bad way; it might be really useful to note these cross-platform similarities.