I've had a G5 for about 6 months now, and it's a great bike. I recently did a ~500 mile trip (150-200 miles a day for 3 days) on it and not a single problem. I had to do a few stints on major freeways on it with a traffic flow going around 80mph, and I definitely had to sit in the slow lane, but was able to do stretches in the 65-70mph range (the speedo tends to read about 5mph fast FYI). However I would say the bike is happiest around the 50mph range, and really you'll have more fun on roads that post speed limits around that anyway.
My fuel economy, handling, and stability all improved when I upped the tire pressure to 24f/32r as is stated on the frame. I tend to get right around 70mpg now. From the dealer the tires were set around 18f/24r (which is what's in the manual), but as many here can attest to, that's too low.
You certainly won't NEED to tinker with the bike every day, though the simplicity of the whole machine might inspire you to
That being said, there is certainly a break in period, actually I would say really 2. The first 500 miles or so you keep it real gentle, I never even went up to 50 at that point and did my best to keep the throttle slow and steady up the gears. After your first oil change, you'll probably need to tighten down a lot of the bolts, fasteners, etc. which will rattle a bit loose at first. You may even lose a few, I lost a couple on my exhaust and the dealer replaced them at that first service. The next 1000-1500 miles or so is the second break in, and here you can increase your speed and aggressiveness on the bike gradually, but it will be constantly still improving it seems.
Other things to watch for, the rear wiring harness seems to be poorly secured from the factory, I and others here have had warranty repairs when it comes loose and gets chewed up on the rear tire. Also watch the heatshield, it seems to have a tendency to come off (just replace the exhaust anyway, the stock one is a power killer and that torpedo tube hanging off the back is a bit unwieldily). Not saying any of this to put you off, if anything you can probably have the dealer check these things ahead of time and have them take care of it before its a problem!
Overall I love this bike, it's exactly what I wanted, and so far seems to be quite reliable.