Given this tidbit, might you reserve an instance now, pay the lower fee, but still take advantage of the new hourly rates on April 1? Or are you locked in at whatever rate your reservation is for?
For example:
Now: m3.xlarge $1266 $0.105 per Hour $1922 $0.086 per Hour
April 1st: m3.xlarge $886 $0.074 per Hour $1345 $0.06 per Hour
It sounds weird if Amazon is actually going to keep charging the higher rate to existing customers, as they've already paid the higher reservation fee as well.
Bummer, though. We just reserved a multi-AZ m3.large RDS instance last week. I wish AWS would take up Google's system of graduated price reductions over steady run duration.
When we switched off EC2 it was financially advantageous to basically give away our heavy instances on the marketplace just to shed the liability.
In this example, it becomes a question of whether it's worth saving $130'ish a year for the liability that a 1-year m3.medium heavy util reservation represents. At the lower end, that's not a huge amount of liability, but it may be a case where I just don't bother reserving m3.mediums anymore because it's a wash.