Well, actually, if you took a mod which didn't use Ace2, then converted it to use Ace2, it is likely that there would be speedups and memory decreases.
Here is a point by point listing of why this is so:
AceLibrary - provides a standardized and full-featured library versioning interface, that minimizes global pollution.
AceOO-2.0 - provides an amazing object orientation interface that is used throughout Ace2. Allows for full featured OOP.
AceComm-2.0 - I wrote this in such a way, that although it is featureful, the data sent across the stream can actually be smaller than the message that you wish to send, due to heavy use of auto-memoization. Also, you can send through arbitrarily long messages of any type, content, or length, and it will get through. It also uses the standardized ChatThrottleLib by Mikk, which other Comm libraries (e.g. Telepathy) also use.
AceConsole-2.0 - Though providing simple print statements, it also provides a featureful framework built on the standardized AceOptions data table, so instead of writing your own haphazard chat handler, it is all done for you.
AceDB-2.0 - The databasing is done in a fast, efficient manner, with profiles already built into the system.
AceEvent-2.0 - For event handling, this is quite fast since it uses and feeds in localized arguments. Also, instead of necessarily using a global OnEvent function, events are efficiently distributed through single messages through a hashing system. For timers and schedules, due to AceEvent's use of a heap and proper sorting, it can actually be much faster overall than using your own throttled OnUpdate handler. It also provides a standardized, fast, and clean interface for inter-addon communication.
AceHook-2.0 - The great thing about AceHook-2.0 compared to manual hooking is the ability to unhook if you are done with a method/function. Granted, if you don't need this feature, then manual hooking may be quite adequate for you.
AceLocale-2.0 - Though one could clearly do proper localization on their own, AceLocale provides many useful (and fast) features, the greatest of which is to have a partial locale that falls back to enUS if a translation is not available. Also, any unused localizations are properly garbage collected as soon as possible, preventing unnecessary memory bloat.
AceModuleCore-2.0 - This provides a handy, featureful module framework that streamlines the module/plugin creation, to allow for a proper, modular structure. Handy if you want to use a project but don't want to use one module, or want to add third-party modules to it.
Now I'm sure that there are many good coders out there, and the way you may be doing it is great, but Ace2 has all these features already available for you, all stress tested and peer reviewed for minimal cpu usage, memory usage, and memory churn, while still remaining highly featureful and useful.
Also, what I listed above is only part of the core Ace2 framework, there are many other great libraries built on top of Ace2.
Dewdrop-2.0 - an amazing dropdown menu library. Imagine blizzard's dropdowns, only without huge memory or CPU loss, but with amazing features, like radio buttons, sliders, edit boxes, and proper updating. Also, this uses the standardized AceOptions data table, so you could actually feed in the same table as what you used for AceConsole-2.0 and have it work like a charm.
Crayon-2.0 - provides coloring capabilities, which covers gradients and flat colors
Abacus-2.0 - advanced time and money formatting.
Babble-2.0 - a collection of localized data covering Spells, Races, Zones, Classes, Spell trees, and Bosses. If you want to know what "The Badlands" are in German (Das Ödland), it'll easily and efficiently tell you. Or if you want to cast "Flash Heal" no matter what locale your user is running in, it'll be there for you. Makes use of AceLocale-2.0.
Deformat-2.0 - lets you efficiently turn format strings and their results back into the original arguments.
FuBarPlugin-2.0 - allows your addon to function as a FuBar plugin.
Gratuity-2.0 - scanning tooltip interface, without all the hassle.
Glory-2.0 - keeps track of nearly all PvP, Honor, and Battlegrounds related info. If you want to know accurately how much Honor you've earned this week, this is the place to turn.
Parser-2.0 - an amazing library that parses chat commands and fires inter-addon events giving proper information. Very helpful.
Roster-2.0 - Keeps track of members in the raid.
MobHealth-3.0 - Calculates the health of a mob.
Tablet-2.0 - An amazing library that creates a tooltip-style display that shows information in a very customizable, fast, and efficient way. Allows you to click on lines if you want, detach tooltips and pin to the screen, etc.
And more.
Feel free to come and hang out with the Ace crew on IRC at irc.freenode.com @ #wowace
Ace2 isn't just about being faster and more efficient, it's also about eliminating redundancy. You shouldn't have to handle your own scheduling, events, hooks, communication, chat handling, localization, saved variables, profiling, etc. Ace2 is there for you to use to make your life easier and to code better addons.