'course, you've gotta expect some guy to weigh in and say that a real man doesn't need no friggin' bucket level indicator....and I guess that'll be me, in the nicest way possible, of course. ;-)
Getting the bucket/forks level is for sure an issue. But it's worth noting that they don't actually get the bucket level, they just get the bottom of the bucket in the same plane as the wheels, which adopt all the imperfections of the ground they're sitting on. Depending on what you're trying to do, this may or may not be helpful.
For each of the machines I've ever used with a FEL, I've set aside some time to have a quasi-religious bonding moment with my machine, whereby I get the machine on level ground and lower the bucket until it's on flat ground (or in neutral cutting attitude) and then memorize exactly what the bucket looks like in that position from the driver's seat, including where the cylinders are in their respective strokes. On my 790, for example, the top of the bucket, which I can see, is basically parallel with the bottom....so there ya go. On my BH, I can tell simply from what the front linkages look like.
And, for excavating or plowing snow, you may or may want the bucket "level". A level indicator won't necessarily help you there, and is likely to be a distraction. Again, this situation arises primarily when your tractor is not on the same grade as your anticipated final grade. For me, it's all about feel---feeling how much the bucket is loading down or not, listening to what the scrape of the bucket sounds like, watching to see if the FEL is binding up, etc. Also, I'll watch immediately behind the bucket to see if I'm scooping up the desired amount of material and make immediate adjustments as required.
As far as the pallet forks go...same kinda issue. I suppose a level indicator would be nice if your pallets were always level where they're sitting....less so if they're not. I always ensure the top of a palleted load appears level, regardless of what the forks are doing.
So, you'll need to develop bucket handling and control skills that are far beyond what a level indicator will give you anyway, so I'd recommend forgoing the distraction of it and just practice. Plus, it'll save you the buyer's remorse when you rip it off or damage it, which you most assuredly will.
Good luck!