What's so bad about the mechlab? Lol I didn't even know this came out, my expectations were so low
It has a pointless "weapons/details" switch on it but that's a minor annoyance. Mech customization is shit at the moment with the base game, instead of equip relying on crit slots to allocate space you have hardlocked hardpoints for various sized equipment. It incorporates the WORST parts of MW4's system and MWO's system. If they had stuck with MWO's system I would probably be complaining a lot less, as at least there I could swap engines if I wanted. There's basically no way to make the vast majority of light mechs worth using for any length of time as they all mount heavy standard engines and move only marginally faster than mediums. Cicadas are absolutely and totally worthless, as are Firestarters, most Locusts (though they ARE Locusts), Urbies, etc. The only mechs I've seen that clearly have XLs are not lights, the class that wrings the most benefit from the XL. I know it's 3015 in-game but not having XLs for lights (or Cicadas/Assassins) makes them really, really bad.
I encountered a bug with the Davion special mission on Mallory's Rift (I suspect this happens elsewhere) where I could not exit my dropship because the damn thing was sunken into the ground, blocking my exit. Save constantly and be prepared to write off entire missions if the mission spawn is bugged.
Advice: get the Hunchbacks whenever you can. Hunchies are good with their STD engines and can carry great payloads and excellent armor for a 50 tonner. They're slow but there is practically ZERO reason to be super fast in this game aside from sheer convenience. Most mechs worth having are not fast. Centurions are OK as well. SRMs spread like crazy, are almost not worth having unless you get Artemis IV enabled SRMs which weigh more. LRMs are really only useful because of their range, they spread heavily unless you luck out and find Streamfire LRMs somewhere. PPCs are godly because they have no minimum range for some reason, but annoying because they cause a sensor interference effect within 90m of wherever they hit EVEN IF THE PPC WAS FIRED BY A FRIENDLY (don't give to teammates unless you like being annoyed by fritzed sensors constantly). AC2s are largely pointless as nothing can boat them in sufficient numbers to achieve proper dakka without sacrificing heavily. The Thunderbolts are reasonably solid heavies, and if you're lucky you'll see some Grasshoppers for sale early on.
Mechs to absolutely avoid purchasing, EVER: Dragon, Shadow Hawk, Wolverine, Assassin, Cicada, pretty much anything Light. There are obviously subpar variants of numerous mechs, but the rule is almost always "More hardpoints, better" as at times there's almost no meaningful distinction between one variant and another other than "less hardpoints". JagerMechs are also bad (though I ROFLstomped enemies with a slightly-tweaked JagerMech-S without the AC2s and with a LOT more armor).
Do not take Defense missions if you can help it. Friendly AIs will mindlessly demolish the buildings you're defending while chasing enemies.
Vagabond camo doesn't work right on the Battlemaster for some reason. No fucking idea why.
You will almost NEVER need more than 2 tons of ammo for your primary weapon TOPS in any mission unless you spray and pray. I have slogged through Warzone missions for many waves and failed to deplete a single ton of AC20 ammo. Ammo is either way too plentiful or just right depending on how you want to look at it I guess.
Store ammo in legs and/or head when possible. Enemies tend to shoot at arms and torsi most often and ammo explosions are goddamned annoying and costly.
Hero mechs are rarely worth it. The Cyclops hero is an exception, as that thing is whoopass on two legs. Swap out the Gauss rifles for AC20s and brawl things to death. The Blackjack hero is funny because LOL Machinegun spam and is surprisingly punchy at its weight because massed MGs do hurt as long as you're in range. The Marauder hero is slow but can dish out ungodly amounts of pain with an AC20 and a bunch of lasers or PPCs.
Missions in general are very repetitive. There are no recon/intel gathering type missions that would reward not smashing things to bits or otherwise being sneaky and fast. Everything is a slugging match, so bring the biggest, slowest stick you can.
Did I mention AI is pretty braindead? Most enemies will mindlessly try to "Circle Of Death" on you to the point where they'll collide with rockfaces and stop dead mid-circle. Mechs with range/speed advantages won't try and keep that advantage - they'll close and brawl just like any other.
Veespam is ridiculous though the only remotely scary things are Manticores and maybe AC5 Partisans. Igors are just damned annoying.
There is another weird bug where some mechs will be damaged by you placing them in Cold Storage.