Some argue that dedicated IPs aren't all that important:
http://blog.postmarkapp.com/post/14127210172/the-false-promi...
While it's true that ISPs and spam filters will take the reputation of neighboring IPs into account, surely having a dedicated IP insulates you from the actions of others better than sharing the exact same address as them.
I agree with the bottom line, though: use an ESP that has a low tolerance for shenanigans.
If the provider is responsive to spam, you've probably got more benefit from their IP block being considered very safe than you'd get from a dedicated IP, and having a dedicated IP doesn't protect you from your ISP's entire range getting flagged if someone else in it goes on a rampage.
ISPs are way more interested in maintaining relationships with ESPs that keep junk from getting to them in the first place than the ones that "quickly fix once the damage is done". It's one case where "asking for forgiveness" isn't preferred over the more careful approach.
SES is more like outsourcing sendmail on your own server so you don't carry the burden of maintaining/securing it, except that you don't have control over it when something goes wrong and you have the same lack of customer support if you don't know how to fix it. If you value your messages getting to the inbox, it's the least desirable option. For sending low-value emails, though, go nuts!