I've never knowingly seen a Pallid Swift. I thought I did several years ago on Rhodes, but then couldn't relocate it amongst the many common swifts with any certainty so it stayed off my Rhodes List, and I went away cursing my poor identification skills compared to those superior birders who effortlessly identify such birds.
Recently there's been lots of fuss on Birdforum about swifts appearing on the east coast. Are they Pallid or Common? Photos have been taken, measurements made, feathers counted, much zooming and rebalancing has gone on, and now we know that they are probably, but not definitely, Pallid Swifts. Suddenly I'm feeling inwardly superior about my earlier caution and generally quite smug.