How (un)stable current version of IC2 is?

i don't know if it's just me, but at the moment all the textures for the blocks are missing (except for the personal safe. I haven't tested useabilit. all I know is that the 4x HV cable works and the night vision goggles don't, all of the items and the boats work though (except for above mention)

I'm going to say stable enough that you can be sure that it won't utterly destroy your world, but you might want to wait a bit longer

I've been experiencing various problems with updates since around build 294. I've actually pulled IC2 and all it's addons until things are better. Hopefully things stabilize soon.

Around build 289 or so they started making compatibility-breaking changes to the API. Using a more-recent version of IC2, with a mod that includes the old API, will lead to problems ... and using a older version of IC2 with a mod that uses the updated API will probably lead to problems too.

Aside from that, your initial premise - include IC2 in the world, but not interact with it aside from worldgen, and *maybe* harvesting ores - seems sound to me. That's what I did, personally - for a long time in 1.5.1, IC2 was just for worldgen. I've since started using many more of the features (each slowly tested, with world backups in advance for when things break horribly) - though I still avoid some of the more classically dangerous areas (crops, nuclear reactors) since something being stable in Build Y does not mean it will be stable in Build Y+1.

For the mods I use, most managed to update their IC2 APIs within a couple days, so that problem didn't last long for me personally. ymmv.

If you just want worldgen, you might want to largely pick one version of IC2 that seems to work for you and mostly just stick with it until you want to start messing with IC2's actual content. That way, you don't need to cautiously re-approach each new release, when you're not interacting with it. But once you do start using the actual content, then staying updated becomes much more important - but you do need to pay attention to the changelogs, and consider whether the changes mentioned seem more likely to fix things or (in the short term) break things.

Since you're on a server, you need to make sure everyone's on the same page about this, though - if *you* know no to mess with X system, but one guy is going to brazenly go after it anyway, that could lead to a lot of problems. And it needs to be clear that when problems do come up (for whatever reason), its largely up to you all to manage and deal with them on your own - support here is going to pretty much be limited to hoping for a kind samaritan in the stickied 1.4.7 beta thread.

Of course, I post that, then run into Forestry needing a more up-to-date copy of IC2 in order to recognize its presence ... and then the updated IC2 brings back the ClassNotFound ic2.api.core.item.ElectricItem NEI crash :p

So it just re-emphasizes that it works, but it takes more active involvement on your part to keep it working.

Last time I tried, almost all events crashed my game.

Same, last time I tried I keep getting crashes (besides no textures being rendered). This is the only mod that I'm waiting to get started playing on 1.5.1

Us redpower-using admins still have to wait another 2-3 weeks for eloraam. If I updated my server and dropped redpower, we would have some mad members. I am already having to drop the "New map" bomb on them.