100% agree with Doug, and my follow up is that if you must use a roll-up screen, then splurge for the tab-tensioned models... Wish there was a manual one though.
There really is nothing wrong with matte white for LCD/DLP, but more effective contrast ratios can be achieved with the grey screens, though some don't like them. I like them a lot.
What is our model of projector that you own?
Is the room a dedicated theater so a fixed screen is an option?
What are you looking to spend on a screen?
I've been using a manaul POS pull down screen for a couple of years and there are definitely wrinkles in it, and every other manual screen that I have seen. I'm longing for a tab-tensioned screen, but that may still be well out of my budget.
If really cheap is what you want, definitely check eBay for some deals as well. When I'm done with my 16:9 screen, that's where it is going and it is truly flawless... the wrinkles were there the day I got it and are there now.