Definitely seconding what Mark said.
I'm still a neophyte at this stuff, but my thinking is that I can get a crap-load of 5% carbon resistors for next to nothing. I *LIKE* knowing I have any resistors I need at any given time without having to make a new order for 3 150k resistors (for example) which invariably leads to me buying a bunch of other stuff to justify the shipping.
On the other hand, I really like having those pretty blue resistors that I know are going to be spot on, especially if it's a build that is expensive/really complex/important.. but I'm not going to pay $0.20 each for them. As Mark suggested, I keep an eye out for lots of them from China or wherever when they're cheap.
That way, out of 30 resistors for a build, if I can manage 25 of them with the 1% metal resistors, and fill in the other 5 with the 5% resistors, I feel pretty good about my overall tolerances without having to know every tiny little detail. Chances are, using nothing but 5% carbon resistors will work fine, but with my tendency towards jacking up even simple builds (yes, I managed to build a non-working CB Naga Viper... fear me...), it's one less thing against me.
One other thing... even though it seems harder for me to differentiate the color bands on the 1% blue resistors, the lighter colored 5% resistors, while easier to read in a perfect world, are often very poorly marked. I have some where the Yellow bands did not print at all, so I had to figure out that a missing color band = Yellow.
Take this all with a grain of salt from someone who is still figuring this stuff out. Just thought a viewpoint from the "still learning" might be worth the input.