I've been using the 1-2 items a month/"plan" way to shop for a little more than a year now and it definitely has changed my closet for the better...though as an impulsive person in general, there's a large part of me that hates the bloodless nature of it!
[And try using this system when every other YLF thread is about the NAS and you've got no money saved up from past months and can't justify "borrowing" from future months, sob/ha!]
Given that I am not a highly organized person by nature, I find it a challenge to keep up with the seasonal closet analysis etc. that this type of shopping seems to demand (from me, anyway).
On the mega-plus side, the system helps me make the most of my clothing budget in two ways: by getting things that work hard for my money; by putting an end to closet orphans. It helps that my style skews more classic, so I don't feel pressure to wear the latest trends.
On the downside, it sucks when I go over one month due to needing basics (March's spring/summer shopping) or even worse, BRAS...the next month of deprivation feels reallllly long, ha.
I definitely have to do what Rosie said to keep from feeling too constrained:
>Within the plan you'd definitely have to build in some fun, inexpensive items, I think.
...usually on costume jewelry!