Clerics aren't the almost-Fighters they used to be (and, truth be told, I always liked Fighter/Cleric multiclassed characters in 2e). Druids are still nature-Clerics, with more offensive spells. Bards seem more their own class, and less "Jack of all trades" characters to me. Somebody in the group said Wizards are uber-powerful, but I've always despised the whole spellbook concept. Is a Sorcerer still a slightly weaker Wizard (I have played a little 3e, for a very brief time)? What the heck is a Warlock?
Everyone but the martial classess (Barbarian, Fighter, Paladin, and Ranger) are "almost-fighter" types now. The wizard can, if his atts allow, fight pretty darned well... My organized play party's wizard has several times turned to his staff... because he had no melee cantrips.
The magic rules have been really overhauled. They're all the same mechanics except warlocks, who are only very slightly different. They're all about as easy to play.
Sorcerers now are just as powerful as wizards... but different. Wildmages are now sorcerers, not wizards.
Wizards are jacks of most spells... everyone is a specialist, but there's no longer a penalty for the opposed school.
Warlocks are the guys who sold their souls for magic. There are about 9 types of warlocks. (Book, Chain, or Blade)*(Great Old One, Fey, or Fiend)... they're almost all direct blasters. They have only a few slots, but those slots are potent, and recharge often.
The Warlock is probably the hardest of the casters, simply because of the low number of slots, and the need to really understand which kind of warlock you are and how to work it. Clerics are amonst the easier ones. They've got one good damage cantrip, and it is pretty potent.
Oh, and fighters come into their own around 5th level. They really start to get badass then.
A rogue needs you near his target.
A barbarian and rogue tag team is HIGHLY lethal (as a troll found out last night.)
Bards know a few spells from every class's list, plus a few unique ones. They can bestow a single-use "inspiration die" on allies, which they can spend to boost a roll they make later.
Bards also boost healing during a short rest (1 hour), and/or provide an after-the-roll-use bonus die in the same rest.
A bard is really freaking awesome. I wish ours would show up again.