To Zen's benefits of water cooling, 1-4 are due to water cooling keeping a more stable operating temperature.Suzuki came up with the air/oil cooled motors to attempt to achieve these same goals, but without as much of a weight penalty as going to water-cooled. The idea was since the engine has to carry oil anyway, add a little more oil, a dual stage oil pump (it pumps high volume, low pressure for cooling duties and low volume, high pressure for rotating parts' bearings), and a bigger oil cooler (racing air-cooled inline 4's were already using coolers anyway) and a few jets to cool things down. This way their bikes would be lighter than the water-cooled competition. This worked for a long time, but eventually, performance parameters needed to stay competitive in racing (and therefore sales) forced a move to water. Now, emissions is forcing it.
As to the benefits of injection, let me be the devil's advocate (I actually like EFI, but it's not all roses) and give some negatives.
To counter #3, there's more electronics. Black boxes, sensors, wires. These aren't always trouble-free and when there's trouble, can be a real headscratcher sometimes - unless you're rich enough to afford shotgun troubleshooting (where you replace anything that might be a problem).
For #4, I don't think there's any difference in fuel economy if the only difference is carbs or a same size & mapped EFI. I've heard reports of it actually going the other way with Harleys.
#5 is debatable, if you're not savy in downloading modified programs and uploading them to your device, but you've been tweaking carbs for decades, carbs may not be as challenging as EFI. OTOH, if you've never tore into a carb and you are well versed in computer technolgy, the reverse is true.
Many carbs can be adjusted with no parts changing, especially for minor changes. If you do jetting yourself (ie, don't buy kits from Ivan, Dale, Dynojet, etc), the cost will be less than tweaking EFI. (I know, cost wasn't mentioned.) EFI will be a matter of swapping a chip (like in old Kawi systems) or simply plugging in a piggyback device like a Power Commander, so that is easier than tearing into carbs to rejet.
To counter #6, that's false. If the carbs are jetted correctly, there's no difference. The caveat is you need to rejet for varying conditions whereas EFI will adjust automatically due to the electronics. An engine is just an air pump. EFI alone will not change how much goes in and how much comes out.
Why so long? That's a good question. It's good to see they're finally doing it though. I do hate to see the finned engines go in naked bikes though. To me, they just look better when they're out there on display with fins. Most water cooled motors look too appliance-like, though there are exceptions where the manufacturer has put fins on their water cooled lumps for stying's sake.