I'm one who does this fairly frequently and have had good luck and bad.
I got Lido deck twice with inside guarantees on Carnival.
RCL I've had the best luck. Once a PR
cabin and once a OV with a inside guarantee. They seem to be much more generous than Carnival who now does upsells so sweet upgrades with guarantees are more rare with Carnival.
I've also done them with Princess and had decent luck.
I like the chance of a upgrade to a higher deck that you do not pay for. I love deals and bargains.
Last time I was below the galley which I would not have picked as I heard it can be noisy, but where I was it was quiet and turned out to be fine.