I voted for "Buy an MBP now." I'll tell you why...While I don't exactly *need* an MBP (I could probably wait for this Fall's merom release, easily), my purchase of an MBP hinges very strongly on my ability sell my 17" Rev.E PB and get good money for it still. Now, I realize around MacRumors I would be hardpressed to find someone who would buy it for $2000+ right now even though it's in mint condition, but on Ebay they still sell for that much and more...
If I were to wait until November (because even if it comes out in Sept. shipping and bugs will keep me waiting a bit), my resale value, and therefore my total spending money, will almost definitely be less.
Problem #2: I have a terrible fear that Apple will completely convert the new Merom MBP's to glossy screens *only*...As in, you don't get a choice between matte and gloss as you do now. That's a major problem for me...major.
Finally, while the Yonah MBP's do have their problems, they are slowly getting fixed...each week you can wait for them, you probably increase your chance of getting a flawless one quite a bit. 64-bit won't do anything for you unless you're a software developer and Merom will undoubtedly have its own share of problems...
So, what you have to ask yourself is: Are you a "first few weeks" purchaser ? If you answered "no," then you're one of those people (I think like most of us) who prefer to sit back and see what the *real* early adopters come up with as far as bugs. That means if Merom comes out in August/September, then you're looking at not purchasing until around November or December...a significantly longer wait than 2 months.
Either way, buy what you want when you want it...If you want to and can wait, then do so...If not, then have at it! Good luck!