Edge is regarded by most as a waste of money. you're always going to pay at least half of full retail, which is always more than the 2 yr contract price.
but more importantly, think about this: Maybe Edge is exactly what you want. Maybe you'll do it for the next 5 years and go thru 5 awesome phones. and then maybe then you'll want to save money and switch to another carrier. Hey, you're not on contract. go ahead. but if you get a high end device that's $700 full, and it's been 1 year, you've paid $350 so far, and you're still gonna owe $350 to cut loose, where as if you went the 2 year contract, you maybe for the phone paid $99 (instead of $350 over 12 months), and the ETF with Verizon will only be $230 so basically, you save, after the ETF, around $370. So Edge is great... for people who plan to keep doing edge/jump/whatever every year until they die, never changing carriers. Oh, and if a carrier (Tmobile) offers to buy out your contract and pay your ETF, guess what? an installment plan is not a termination fee. you're on your own, buddy. I'm not trying to sound overly dramatic, but that's the math, man.
finally, Edge is NOT "pay nothing up front". you pay tax on the full price, and you pay the first month's payment up front as well. since you're always billed one month in advance with Verizon, if you didn't pay the first month in store, you next bill would be 2 months worth of payments. Carriers take the first month up front to prevent bill-shock
so that's my feelings towards edge (I used to work in the Cell industry. quit late last year.). As for the M8, this phone rules. why? there's 1000 reviews already out there, so I'm not gonna bother with the why.