It should hold up like a regular dining table does. It will likely show wear but in that patina a beautiful family collection of memories will be held.

You want to watch out if you have a sink in the island. At least in my house, the area around the faucet often stays wet, because every time you turn off the faucet with wet hands or use a sponge, there's a drip or two.

What is your capacity for embracing patina and a not new look? I'd think that with reclaimed wood, that is the name of the game, that you'd want to see age over time.

We have both a reclaimed Douglas fir dining table and a beech butcherblock countertop finished in Waterlox. Depending on what type of pine you are considering, fir may be more or less soft. We eat at the dining table two meals a day (with kids) so it does get heavy use. A lot depends on how pristine you want your counter to look, and also how much you are willing to sand down the reclaimed wood. When we bought our table, we had a choice of a number of levels of "distressed" and chose one at the mid-point, which meant it would have some remaining knots and nail holes and some filler (I think there were options for both clear resin-style filler and also color-matched filler depending on the desired look). If you run your hand across it, it is not smooth. If we had gone with a less distressed finish the place that made it would have sanded it down further and filled more if the holes for a smoother finish that would have been more crumb-resistant but less "reclaimed wood" in appearance. With some divots and less filler, it 100% does get messy with daily use and crumbs get lodged in the crevices. I don't think I'd want to use it as a kitchen work space but I don't mind it for eating meals at—so it also depends on how you plan to use your island. We also aren't fussy about appearances, so if you are, you'll either want to sand it down considerably so it can be cleanly wiped—with ours, the sponge often catches on the crevices—or fill some of the imperfections (or just choose a different option entirely). The beech counter is definitely more bulletproof and much better suited to be a prep counter, but has far less character.

Reclaimed wood table (after 18 years of daily use):

I’ve had a large maple butcher block top on my island since 1986. I’ve used Boos Wood cream on it. It has held up just fine.

If it is a plank top, then you will get separations between the planks, and crumbs and yuck stuck in between. It would have to be a laid up piece of alternating grain direction or end grain material, to not have so much standard shrinking and swelling of the wood that it would split. IT takes a top notch cabinet guy or woodworker to do something you won't regret.

Choosing "reclaimed old wood" implies you embrace and welcome wood grain and feel, developing wear, growing patina over time. If that's not the case, and you're going to flip out over every new mark, stain, etc, then you can finish with polyurethane for what will feel like and essentially be a plastic countertop. If you want the feel of wood not plastic, then read on.

The main issue will be staining, like if coffee, red wine, soy sauce, other nasties are left on the top for hours or overnight. I tested Waterlox and some other finishes for stain resistance on maple, results in this (very long and rambly, you'll have to scroll to about halfway through to find it) thread. Musings On Calorie Restriction Cooking Waterlox was pretty resistant but not impervious to these things left on for 12 hours, although that is a severe test - would you really let a puddle of soy sauce stay overnight? - and if you apply many coats and let each dry longer than I did, your results may well be better.

Going back to what you embrace - even in my 12 hour test, the staining on Waterlox was not major in my view, and I think the spots could be sanded out then refinished. So even if soy sauce is occasionally spilled and left alone overnight, it is not a big deal if you have or are willing to buy a $40 orbital sander and do some work, maybe every several years, maybe never. So, if all you have is Waterlox, I'd go ahead and use it. If you are willing to order and test for yourself the other products mentioned in the thread, that might be an option.

I should say after doing those tests, I used hard maple butcherblock for my counters, two finished with Osmo, and they've held up well, including to big coffee spills from a leaking machine. Not "spotless" but probably no-one but me would notice any discoloration. I've lightly sanded (by hand) and refinished a couple spots, but it wasn't necessary, just me wanting to see what would happen. The third counter is finished with mineral oil/wax and, as expected, has picked up noticeable stains. I don't care, it is an unpretty working kitchen, but someday I may flip that block over and finish the new surface with Osmo.

I had a reclaimed wood dining table and hated it. I was fine with the patina, but not with the crumbs that got into every nook and cranny. But it was a plank-top, so had lots of grain and surface imperfections. I now have an oil-finished butcher block island top (new, not reclaimed) and love it.

I used Waterlox on an old table with two very wide boards that I use as an island in the kitchen some 20 years ago. Water still beads up on it and it looks great.