With Freedom and Dispels I think BM is an inferior Arena spec. It's nice for burst teams where you need to drop someone (and avoid being dropped) in the first 15-20 seconds of a Battle, but beyond that it becomes a weak MM with a 2 minute cooldown. Marksman brings much more utility and pure personal DPS that does not rely on keeping a 6k health, zero resilience pet alive at all times to use their key abilities. BM is a great anti-melee and dueling spec, the unfortunate thing is that once he uses Bestial Wrath, he's basically shit outta luck for the next two minutes. It comes down to timers - and for 5s, Marksman has more of them available at any given time. To be perfectly honest, you may find Cyclone being your one and only dependable CC on that team to be lackluster when facing 2345 teams.

100 haste = ~6% cast/GCD reduction or in terms of Wrath = ~1.4sec, Starfire ~2.8sec. Moonkin with 200 haste and 1k spell damage will be some killing machine!

I have very similar experience on my 5s teams. I rarely play more than 10 games a week (not by choice) so I don't have THAT much experience but 'Jack of all trades, Master of none' pretty much describes the Balance specs. I've tried 42/11/8, 46/0/15 and even went resto with the Wyrmhide set to see what all the QQing was about.

42/11/8 gives you the ranged interrupt with feral charge - but it's not instant, it takes the GCD to get off. Problem with the spec is that it is extremely mana inefficient, even after the patch. The most successful 5s team I was on was 4 dps and we only got to 1750. Felguard lock/ele sham/Moonkin/MS war/HPally (the lock changed his spec frequently going from Felguard to SL/SL) and I ran the 46/0/15 spec. ALL of your points ring too true to my liking . I've been used instead of a mage in a 2345 team but the lack of counterspell made it hard to finish off a target.

Compare as we dare, Balance druid to Frost mage;
-For melee we bring roots - mages bring nova and frostbite
-For general CC we bring cyclone - mages bring sheep (interesting though is that druids are the best at CCing druids with hibernate and no immunity to cyclone in any form) Now however, with only a 20yrd range on cyclone and a duration that is almost half and a far less forgiving DR, polymorph is just a better CC. EDIT Then there's counterspell for mages. How many matches have been won or lost by a pally being counterspelled at just the right time?
-For DPS...well even with the 2.4 set bonuses, a Moonkin can't match a shatter combo for pure burst. It has improved mind you.
-For survivability we have great physical dmg mitigation but the only defense we get to magic is from our resists (woo hoo go go MoTW!) and BoP for the 4% spell avoidance - Mages have a few tricks up their sleeve with iceblock, frost barrier, mana shield and blink, heh even Blazing Speed for the weird mage specs. They also have the fire and frost shields vs. some types of spell damage and ice armor helps alot for getting away from melee.
-For lasting power we have Innervate and cheetah to run away and drink - Mages have mana gems and evocation.
*We can heal. Mages can't.

All in all we look almost equal on paper. But in fact it doesn't feel that way. I have a 70 frost mage with under +500 spell dmg and I do surprisingly well compared to my Moonkin in BGs. It feels like I need much less skill and gear to make an impression as a mage than I do as a Moonkin. So if I were on a competitive team, I would rather have a mage than a Balance druid simply because the mage doesn't have to be stellar for it to work but the Moonkin does.

A question was asked earlier about Haste effecting the GCD on shapeshifting - has anyone tested this?

The MSD provides 320 haste for 3 seconds and I've found it more useful when healing than when DPSing. Getting a 3 stack of lifebloom up in about 3.5 seconds is great. But with NG + Wrath of Elune and Focus procced, .8 second Starfires are nice...especially when it stuns

I think a druid's biggest advantage towards a mage would be that he's focused after the mage, presuming that he starts in stealth... in fact, I'm curious, how does our boomkin friends start the games?

I tried a few games as Moonkin/Rogue and Moonkin/Rogue/Lock. In 3s, they always focused the lock; in 2s, I was almost always the focus. (1600-1700 rating) Wearing PvE gear worked well in 3s, but it backfired once we queued for two's. I was starting in stealth and popping out as soon as the rogue. If we do it again, I will wait much longer in stealth, as if I was resto.

Does anybody know if they're adding a new Belt/Bracers/Boots/Jewelery set with S4? I'm currently gearing out a balance druid for PvP stuff...but I don't want to be buying the Vindicator's gear if it turns out that there'll be an S4 set with better stats (adding crit., or so on..).

Very good point. Arena is about control, and moonkin are 'wild'.

As for starting a match, it depends who I'm partnered with, and what we are fighting. If it's magic heavy I try to stay stealthed until the Cyclone on the healer is needed...at least I used to. Haven't done too much arena since the cyclone nerf. Generally if they're melee heavy I pop into Moonkin form early hoping they target me, other wise I wait for their stealth to pop so I can stun him to give who ever they are trying to gank some breathing room. The more I play the more "It depends" is the answer to questions. There is no right way to do it. It always depends on the circumstances.

Do you know any addons that help me recognizing the proc of the new PvP-Set? I often find myself misstiming my Starfires because I didn't notice the proc in the heat of the battle. Even worse: Interrupting the 1.5 sec Starfire will still consume the proc. Is that intended?

If you turn on "Auras" in Interface Options --> Combat Text, "<Wrath of Elune>" will float by your toon every time you get the buff. I'm sure addons work as well, but this has been enough for me.

I use Power Auras and set it to look for Wrath of Elune and Nature's Grace. If you pick a big aura graphic and pick a nice bright color, you'll see the buff even before your Wrath lands so you can stop spamming wrath even before the GCD is ready. Saves alot of time.

Always thought that 5 of one class would be quite nasty, I heard once of 4 warlocks and a shadow priest, 2 locks were unstable affliction and the other 2 demo, it was unreal the amount of damage from the DoTs and became unhealable due to the UA with the felguards charging and cleaving the healers...

Also heard of a 5 Boomkin team, seen a few in action on youtube, it was moonfire, entangle, cyclone, travel form run away entangle heal up boomkin, sort of things, some of them were quite funny where they'd just sit in the entrance and dance!

I was planning on going feral and raiding with my druid, but thinking more of getting into the arena as a out of mana kin!