Well that's 30 caps for $6 plus shipping. comes out to $0.20 per cap. you may find you're already getting a better deal buying individually without the shipping weight of the container...or maybe you want the container for better organization.
Then, 250V caps might be physically larger than your standard issue 25V ones...may not fit on a layout.
My current answer to stocking up on parts (I see you asked the question last year) is lookey here for the most popular values:
http://diy-fever.com/misc/value-statistics/Will your next build even use mostly the values in the assortment?
Frankly, the way I'd do it is buy all the caps--
separately--for the next 3 or so circuits you're gonna build. That way you get what you want and what yer circuit
needs. Throw in a few extra of the values you see yourself ordering a bunch of. You're not really saving much by getting that assortment but it might be less of a hassle.