I don't think it's worth it to order an ultra-premium vodka for a mixed drink, especially for something like a bloody mary. After you add the tomato juice, worstershire, tabasco, salt, pepper, lime, etc., I can't taste the difference between Grey Goose and Smirnoff.
I agree with you on Mojitos though. When made properly, they are the perfect warm-weather concoction.
I've become too good a bartender at home, I guess. I'm typically disappointed when someone else makes my drinks. I prefer the old-school martini made with either Chopin vodka or Bombay gin, a twist (no olive), and just a drop of Vermouth. The key to the drink is that it has to be crackling ice cold.
My wife goes for more of the frou frou stuff, and these days I sometimes make her something that tastes great, but also is the coolest looking drink ever.
Start by mixing equal parts Ketel One (or any other mid-range good vodka) with Rose's sweet and sour mix. Shake with ice and strain it into a martini glass. Then take a shotglass full of Chambord (a french raspberry liqueur) and pour it down the side of the martini glass so it layers at the bottom of the glass without mixing. Then add a fresh raspberry as a garnish. It's way too sweet for my taste, but chicks (pardon the chauvanism) love it, and it's got a great 2-tone layered look that makes it a great "special occasion" drink.
Sorry for rambling, but I really enjoy the art of good bartending, and when I go out somewhere that charges me $12 or so for a premium cocktail, I think some care should go into making it properly.