Same here, I've played the beta for about 20 games or so.
xterm already noted the main differences betwen HotS and Dota/LoL, here are a few to add:
- Games are considerably shorter
- You need to buy heroes (with a periodic rotation of free ones), similarly to LoL
- It inherits from the Blizzard lore. If you play Diablo/Starcraft/(World of )Warcraft, you'll meet familiar characters.
- Better tutorial, and overall single player experience
- You can't win without properly managing the objectives of the map you're playing.
This should be the case in Dota too :P