Replaced the brake lines (front and rear) with Galfer stainless...they were < $100 for the set (brand new), and Suzuki recommends replacing the OEM rubber lines every 5 years (they were probably the originals, and I have an '04). Also, the Galfer claim that they include mounting brackets is a complete lie. There were no brackets in the kit, so with some minor modifications to the old ones I have some of the lines supported permanently. Zip ties are retaining the 2nd line and speedo cable for the time being, until I can obtain some proper metal/rubber p-clamps.
Fresh DOT 4 all around, and I had no problems at all getting them to bleed using conventional means. I'm not sure why everyone thinks you need some special banjo bolt, etc. I used a vac pump on the caliper bleed screws to suck fluid down from the reservoir, which also flushed out the calipers. The old fluid may have been original, it was fairly brown.
The brake levers definitely feel much firmer than before. This is good and bad...the bad being that squishy brake lines are more forgiving if you grab a fistful of brake in a panic, and they will also smoothen out small vibrations while braking better. I'm generally very deliberate with my braking modulation, and so far no unusual pulsation.
I also put some RTV on the backside of the rear pads, which got rid of the annoying brake squeaking I've had ever since remounting the rear wheel.
Still on the to-do (probably for when riding season is over) is a fork oil change, and possibly slightly stiffer springs up front. I also need to do some minor rear shock dampening and preload tuning (2014 ZX-14R shock/spring), but being that 99% of my commute is straight highways, it's difficult to gauge what, if anything, needs adjustment.