Hey, if your corp had joined IRON you might see me in allied fleets (I'm in RZR now ^^)

Lag makes large-scale engagements unfeasible, most of the time. Yesterday, for instance, we had a Mexican standoff with BoB since no side was prepared to jump to the other... so our large fleet was on one side of the gate, and a similar sized BoB one on the other. But lag made jumping not an option for either side :/
Similarly, when Shrike was tackled in 49- a few months ago, grid didn't load for me until the node crashed - I didn't even know whether I was on the gate within DD range, or had warped to a POS.
I've lost battleships to hostiles I couldn't see, or because my game was so lagged that I was unable to MWD out of a bubble because my ship wouldn't respond to commands until it was too late.
Fleet fights can be great fun, but it's really the luck of the draw as to how much lag will affect you. It's no fun when primaries called by your FC don't load for you until they explode, or when your guns don't activate until the target is already dead.
Small roaming gangs, with current game mechanics, require speed to survive, and roaming gangs are where most of the fun in game is. Nanoships can be countered - rapiers/huginns, and to a lesser extend curses, are pretty effective at that. Applying more severe stacking penalties to overdrives so that speed doesn't just come down to which ship has the most low slots, bringing polycarb bonuses in line with other rigs, adjusting the bonus given by pirate implants (or adjusting loot tables so snake drops become very rare indeed) - all these would have done something to address excessive speed while still keeping speed ships viable.
And what exactly is excessive? Why shouldn't a faction fitted interceptor with maxed out skills, snakes and a command ship bonus go >20km/s, given the amount of skills and isk invested in such a ship? Yeah, vagabonds and nano ishtars can be annoying - but they die a lot too.
In 0.0, unless you bring superior numbers - which more often than not means lag, lag and more lag - you need to be able to move fast, hit & run. I would really miss it if fast roaming gangs were no longer possible - and when the opponent may have jump bridges or hotdrop caps on your gang, then they effectively bypass the speed nerf :/