With proper planning, most combats won't last past the first combat turn or two (most of my group's combats are done before the end of the first combat turn). Not all of my players are real secure feeling with the rules, so I haven't implemented the ten second rule at my table, but when it's in effect, combat can easily be as quick as other aspects of the game.
Having low IPs sucks, but it isn't impossible to compete without them, you just have to be smart. Likewise, teamwork is essential. That technomancer, for instance, might not be able to do anything in combat himself, but he could always edit his feed to highlight the enemy targets and send the feed to his buddies giving them an AR assist bonus. Likewise, a mage could easily cast Increased Reflexes on a unwired mundane to speed him along.
I don't think the Initiative boosters really impact variety that much. You have three different types of augmentations, magic, and drugs to choose from, all with multiple ratings. A 2 IP character can still compete with 3 IP characters if he needs too, he just has to be smart about it (taking cover for instance). Even if every single player takes Wired Ref. 2, that still leaves 3 points of essence to play around with, and there is a lot of variety to be had within those three points. You generally see less variation in the spells of combat mages than you'll see in those points of ware.