Some weeks ago I switched from Firefox to Safari. While Safari is -- in my experience -- quicker, better looking, and has Top Sites, I was also missing some functionality of firefox. To be more precise, I missed the 'search when start typing' option, and the fact that you can automatically search by typing something in the location bar.
For both problems I found a solution, respectively Safari Stand and keywurl (keywurl hasn't been updated to snow leopard at this moment 10/2/09). So, if you like safari better than firefox, but are missing those functions, make sure to download these great tools!