I generally avoid Open now due to various issues I've had when instancing with others. My PC and connection are both pretty good, and I can team up with a few friends - who also have a decent set-up - and we can play for hours, SLF's deployed, without a snag. Had another commander turn up in a HazRes one time, and it all went to poop. FPS remained unchanged, but teleporting ships, hits not counting etc. became rife. Had to quit the instance. Another time, I was in open and got interdicted and the entire instance went screwy, ship jumping around (teleporting / rubber banding) damage not counting, then massive damage being applied (game catching up?) then it ended in a partial UI freeze, requiring a menu log as I was no longer technically playing the game.
I know a poor connection / poor PC can literally break an instance when that player turns up. We experienced it first hand when my regular team mate had some internet issues, we could not instance together without it being glitch city. Once he got those issues resolved, all was well. With no other players around, his game experience was fine, once other players were involved, everything went to poop.
If we're going to team up for any reason now, we'll generally just go into a Private Group of just us. Works great, no surprises.
It's a shame the game doesn't "see" when a particular player has degraded the experience like this, and automatically pop them into their own instance.
Note: we've found that Ping / Latency is key for a smooth experience. Even when I was on pretty terrible rural Broadband (only BB in name!) with about 2.5mbps down and 1mbps up, my experience was still generally good. However, when a friend had like 100mbps/40mbps but poor latency, the experience was terrible.
Note 2: I know some people have had issues while they're playing, but others in the house (spouse, kids, house mates etc.) have started doing something (Streaming?) and their game experience has degraded.