We just moved our DNS from Network Solutions to Route 53 this month, and I can verify that there are indeed resolvers that'll ignore TTLs. Ours were 3-6 hours, but it took some sites about 24 hours to pick up our new SOA.

Which would have been fine - the A records were the same - but no, NetSol instantly starts serving a blank "Business Profile" landing page A-record. Thanks, people who used to run the Internet.

I know one such caching server was ns1.dns.rcn.net. (But only from inside RCN; querying it from Comcast gave different results. Same IP address, so I'm assuming it's anycast.) whatsmydns.net reported others as "Bell South" and "Cox" (I can't recall the locations, I think one was in Georgia).