No denying is the biggest single change, of course.
The power of the champions is way lower, too. Stuns are hard to come by, unlike DotA where everyone has a 3 second stun/disable. There's a lot of skill shots in the game, which is unlike DotA - the more powerful disables/stuns do not auto-hit and need to be aimed.
Towers in LoL hit way harder and LoL has brush where you can hide.
There are a lot of direct ripoff champions, which is to be expected:
Drow Ranger = Ashe (except Ashe is awesome and Traxex was horrible when I played)
Stealth Assassin = Akali (again Akali is far better in this game)
Phantom Lancer = Shaco
Mordekaiser's ult is the same as Doom from DotA (can't remember the hero who had that) and Galio and Nunu have similar ults to Enigma's "black hole" ult (though not nearly as good).
That's all I can think of off the top of my head, but Riot Games put together this page that helps explain the differences too:
http://www.leagueoflegends.com/learn/dota_and_lol