I just picked up the Dungeon Crawl Classics Role-Playing Game last week and I have to say that I fucking love it! I'll write an actual review which will be forthcoming.
For now, I've just finished reading through the whole thing and I can say that my desire to modify the game via house rule is minimal. Apart from letting PCs start their 0-level characters with maximum Hit Points, I think wizards should start with the Invoke Patron and Patron Bond spells. These, and other spells their Patron may bestow upon the wizard, would never count against the wizard's maximum number of known spells.
I'm currently GMing a Saturday group (Stars Without Number) and playing in a Sunday group (about to start Call of Cthulhu 6th edition), but whenever I get my next chance to GM a fresh game, DCC RPG is what I'll be running.