I played the beta extensively on the X1. Totally fell in love with the story, environment and PvE aspects. The gunplay felt solid and responsive. I especially liked that gear, at the green level and up, had skill trees you unlocked by using the weapons. Heck, even the armor, green rarity and above, had additional bonuses you got. Great thing was I went and looked at the vendors and the level 20 legendary (purple -- and there is a tier above legendary too) had some long skill trees to work with and the final stage was "Increase Damage, but lock in all previous choices." So one had best be sure they have that weapon set up the way one wants them.
The PvP was, well, chaotic and random. At times it was a very empowering experience at others it was an exercise in frustration. It didn't help that one PvP map, the moon, was quite possibly the worst map I've played in a number of years. The Venus map, Shores of Time, was actually pretty good and suited to the Control mode (think Hardpoint Dom from CoD.) While the PvP is hectic and even fun at times, it needs a massive amount of balancing for any longevity.
Strikes. Oh my. I did the Devil's Lair a good 15 times across 2 characters, a Titan and a Warlock. So much fun and far and away the best experience I've had on the new gen of consoles, or for a long time in a fps for that matter. Strikes require the fire team (group of 3) to be coordinating well and taking down priority targets as they appear or risk getting over-run. All the footage shown of The Devil's Lair is from the first 1/3 of the strike. However, it doesn't quite show, or do justice to, the amount of enemies in that room that spawn and how hectic it can be. Very rewarding finishing that first phase.
2nd encounter of the Devil's Lair is a small room with mook mobs, followed by a Devil Walker and a lot of adds. The Devil Walker has 2 attacks that can ruin your day instantly, so it requires the players to have situational awareness, coordinate between the fire team members and be on their toes for incoming attacks from the Walker. The fight does have adds at certain stages and they must be managed. It is a much more challenging encounter for a team of 3 versus the open world Devil Walker Event. After the walker is the actual boss, Sepiks Prime. There are adds in that fight and it's really a tank/dps/manage agro fight that most MMOer's know quite well. There is also a lot of room to move around in the arena with plenty of cover and 3 levels of the arena. All in all If all the strikes and raids are of this level of quality, balance and fun then these encounters will be things one goes back to often. There were also 2 modes for it normal and hard.
All that said, I had a blast being part of an event that is not an actual community event in the overworld. In the middle area between two underground portions of a zone called Skywatch. The Hive and the Fallen are fighting between each other non stop normally and these are a couple of groups of each. Watching this part makes you realize the Fallen and Hive are deadlocked. At noon, or midnight, in game the battle escalates to an all out war where each sides numbers just start growing in an attempt to break the stalemate. What started out as some level 5 and 6 Fallen and Hive turn quickly into level 7 and 8 Fallen and Hive Ultra's and Majors that just go ham on each other for about 5-6 minutes. Of course, this "event" quickly turns into a rather large number of enemies on screen. These higher level, tougher mobs keep spawning infinitely until a specific time then they retreat back to their starting points and the normal mobs take up the fight again. Oh course, the players can get involved and this will make both the Fallen and Hive target you as well as each other. So much fun and definitely one of those "Oh wow, this is awesome!" moments from the beta that everyone should have had.
All in all Destiny is quite good, but can still improve in a number of areas. If you go in expecting Halo 2.0 you are going to be disappointed, especially if you are doing it for PvP.