From what I have heard (but haven't played as I'm not in the Beta), I'm undecided. Most people who have played the Beta do say that it feels like an evolved version of Halo, which I consider a good thing. My personal concern, however, is with the jetpack. To me that is the one added element that really doesn't "feel" like Halo at all. It does sound as if they are balancing the Jetpack out to some extent by limiting it's use and making falling damage deadly, but I still can't help but gag a little at the thought.
I suppose I'm also a little concerned by the focus on team objective based modes in the Beta as I've always sort of equated Halo multiplayer with Slayer mode and little else... but I guess there's other modes in Halo1/2/3 and Slayer was always the focus of the players there anyway.