Citrus tetraploids typically display a little bit more cold tolerance and have slightly larger leaf and flower size.
However, they do not set quite as much fruit as normal diploids.
Tetraploid versions of diploid species are very common in the plant world, and with garden cultivars.
In fact, this is believed to be one of the possible routes of speciation, when a plant spontaneously doubles its number of chromosomes and then that leads to a reproductive barrier with the rest of the species gene pool (because the mixed offspring between the two groups, triploids, typically have marked decrease in fertility). There's even one example of this among citrus, the Hong Kong kumquat.