Finally have a chance to post some impressions. The Halo gods provided this mortal with a code on Friday after all but alas, Eazy and Ghaleon always had full parties when I was on :| Onto impressions:
My greatest criticisms/bitching in Halo 3 were the extremely broken melee system, grenade spamming, and the rank system. It just made 0 sense that the experience went off of team wins rather than individual performance when the whole point is to match against equal level players. In comes Reach, fixing 2 out of 3 (kinda)
The melee system in Reach provides a truly level playing field, you either take down all their shield and hit, or get in two smacks before they strike you down. There's no more random 'I shot him a few times and melee'd and all he did was melee once' scenarios.
The rank system is finally focused on performance, you get jack squat for merely winning a match but if you play well and primarily, earn lots of medals, you receive your just rewards. It's still not perfect, I've had games where I captured 7 flags in stockpile with +9 k/d on top of that and still barely got any experience. This is where my "kinda" comment comes in. It seems as though they just based it off of total medals/what type of medals which unfortunatley, isn't the most accurate way to determine if someone played well. It also could encourage people to not focus on the win and just run around trying to sticky and beat down people for more medals. The system needs to account for the objective in a match, and base your xp on how well you performed. This means that k/d ratio shouldn't be the primary factor in capture the flag (maybe an extra level of points at best for k/d ratio). All in all though, it was far less frustrating getting good experience when I played well despite losing a match because someone on my team recieved a whopping 2 kills.
As for weapons, I'm pleasantly surprised. I never thought I'd get over the BR but I'm pretty pleased with the DMR. I'm not saying it's as good as the BR, but it's more balanced. Nothing illustrates this as well as SWAT. In Halo 3, it came down to who pressed the button quicker/had a better connection. In Reach, it comes down to who is more skilled with the DMR. There's less auto-aim and it's clear playing against different skill-leveled opponents, that there is far more of a learning curve with this rifle than the BR. That said, anyone that was skilled with the BR should feel right at home with this weapon, it was a pretty seamless transition for me. The needler rifle works out well and isn't OP like I believed it would be at all. The pistol is great and really rewards you for proper marksmanship. I honestly don't see any reason to use the AR, ever. I'm glad the AR is in because I believe in options for different gamers, but having the pistol as a secondary suits my tastes well. I have to admit, however that I am already pining for DMR starts. The focus rifle is a pretty awesome weapon and more noob friendly than the other rifles. Shotgun seems easier to use, more powerful. I really dig the ability to block the sword with melee

This gives you chance to out play a hack and slasher but the sword wielder can still get in a second swipe faster than you can block again so only skilled players will be rewarded. Great balance. The one weapon that seems overpowered to me is the plasma grenade launcher. Locks on AND stickies you? You get hit, your dead, period and that in itself might not be overly powered if it wasn't for the ability to lock on.... My recomendation is that the lock on ability be removed.
Grenades. REDUCE THEM. Spamming is worse than ever with the increased grenade damage. If you want to increase their damage output, fine, but for the love of god remove them from maps and don't allow people to pick them off of corpses. They truly are power weapons with the new damage increase and should be treated as such, in limited supply. It's absurd that you can collect a never ending supply of these things.
Armor Abilities: Fantastic. This addition really adds an extra layer of depth to the battles and makes you consider how you want to approach different objectives. I wondered if being able to swap them every respawn would be a good idea but after playing, I do. It allows you to adapt to a recent development and keeps the gameplay fresh. Perhaps you chose invis so that you could camp with rockets near the flag your protecting at the start of the match but eventually you are killed and the flag is taken. Time to switch to a jetpack or sprint so you can chase the thief down. My primary criticism for AA's is the Armor Lock. This thing needs to have the cooldown increased! It's ridiculous that you can do a full charged armor lock and literally a couple of seconds later, do another full charge. It gives the other person 2-3 seconds to kill them before they lock down again. I have no problem with it's ability, just increase the cooldown time.
Veto system: Awesome. No more will you veto a gametype you hate, only to blindly get something worse. You have serious options now and that's fantastic. The one thing that needs to be fixed is that it takes way too many presses of the 'B' button to back out of some of the stat menues to get to the veto screen. It's my firm belief that this is the primary cause of so many people seemingly not paying attention and voting on anything, thus resulting in the top selection so often. Is there some way to tweak it so that you can bounce back to the veto screen in a moments notice (when you hear the audio queue ticking off)? Perhaps hold down on the B buttion for a second to bounce all the way back.
So far I'm pretty damn happy with what I've seen and with a few tweaks, this can truly be a great game. I can already tell that I will enjoy this installation more than 3. Great job Bungiee and hopefully the concerns you see arise frequently will go under your consideration to change for the full release.