Just finished a playthrough on Insane. All in all, not too bad! The main campaign is surprisingly well-balanced for that difficulty.
A few interesting observations, all running counter to the idea that a) capital ships are easy to kill, b) Alpha 1 is god, and c) Shivans have only crap ships.
1) Having a fighter on your tail is serious business.
1a) Having a Nahema on your tail is awful. Who knew that ship was such a good dogfighter? And it can outrun...everything. Once, on Argonautica, one just hung off my Perseus' tail and dropped me from 100/full shields to 8/no shields.
1b) Having a Nephilim on your tail is just hell. It can't usually stay there very well, but it if it does - yowch.
1c) You should never fly in front of a Seraphim formation.
1d) The Astaroth doesn't suck as much as I thought. The Mara is more than solid. The Dragon deserves its reputation -- I saw one last a good ten seconds while being C31ed by four Kayser-armed friendly wings. If these carried better weaponry they'd be really irritating. Shivan fighters seem to be very specialized, and while they don't do well outside their roles, they're pretty decent within them.
2)Attacking even the smallest capital ship is risky business. This is due to AAA beams. Flak makes it exponentially worse against destroyers. Blobs aren't generally a serious threat unless your shields are down.
2a) Flak is hell. Bomber crews must have an ungodly casualty rate.
3) Allied Command has pretty good tactics. Command is not dumb. Recon elements do a lot of good spotting in the FS2 campaign, and friendly warships are (generally) employed well.
4) Speaking of command, the last few missions of the FS2 campaign are really superb at making you feel like a squadron leader. More than any previous mission, they depend on your guard assignments and orders. I felt really cool on 'Clash of the Titans', telling various wings to guard each cruiser and then setting Gamma after each inbound bomber wing. 'Apocalypse' requires you to identify the critical targets the Shivans are going after and focus your protection on them. Fun stuff.
5) The Infyrno isn't junk. If you could carry a few more, it'd be my anti-bomber weapon of choice. You can take out entire formations with one hit.
It's cool that I'm still getting new stuff out of this game after ten years of play.