It should be noted that the Sudden [Metamagic] Feats are also applicable to Invocations (including Eldritch Blast, obviously). They're not, clearly, as good as the [Metamagic] Spell-Like Ability Feats in the long run, but if you're only playing a low-level game (e.g. in an E6 environment), then they can provide a little boost that would otherwise be unavailable (bearing in mind that Blast Essences and Blast Shapes increase the CL of your Blast...so a Chain Blast, for example, cannot be used Maximised until you are level 10? 12? I forget and am away from books, but it's something up there). In addition, you do not have to specify the Invocation a Sudden [Metamagic] Feat applies to, potentially giving you a little more flexibility. Alternatively, they can be used to apply metamagic to your Invocations at low levels, then be re-trained out for their 3/day counterpart when you get to a sufficiently high level.