Bit of advice, turn on the Grunt birthday party skull. It really helps to know you've definitely got them. And just generally aim for headshots - Covie carbine and light rifle are your best friends.
My issue with the first half is, it's visually great - but the battles are quite standard for the series, and not very epic. Then the second half has amazing parts like Composer, which is why I play Halo. The first half kinda ticks along, but the second half has set pieces in big sandboxes, and I love that.
I mean, the latter half has the Mammoth, a Pelican you can fly, the massive Mantis sandbox battle on a moon base, and that awesome Afterburner trench run. What's not to love?
Speaking of which, I'm hoping for some better vehicular action in Ops 2. A ride like Mission 5 or a repeat of that Composer sandbox would be great.
I need to retry Lone Wolf, as my first attempt was not long after my first finish and I was AWFUL. Like, stuck on the bit just after the Elite/2 Grunts/2 Jackals battle bad. Reach was a real slog that I eventually got through, and I just don't know if I can be bothered this time.