zkyevolved, for fast typing, your solution is far preferable. (My Personal Menu/xte solution is really just for form filling; and admittedly it is cumbersome.) Heck with wanting autotext for the N900:

I want autotext for Diablo! For the N800 and N810! I hope it at least gets into Mer.

In the old Macintosh OS (Mac OS 7; probably through OS 9), there was a program you could install called "Thunder 7," which enabled auto-correction across all the programs. I used to use it like you use the Blackberry auto-correct, but less extensively. (I had a full keyboard, of course; so I used it just for long words, like "rel" for "relationship" and, for a specific paper, "anth" for "anthropomorphic.")

So for the old Mac, there was Thunder 7. Googling for a program that applies customizable auto-correct uniformly across all programs on current OSes, I've come up with PhraseExpress, FastFox typing Expander and JitBit AutoText, all of which are commercial programs. There doesn't even appear to be a comprehensive AutoText app for the iPhone.

Interestingly, I found that there are a number of requests for an AutoText Add-On for FireFox, but none seem to have been created. If the N900's browser could take Firefox add-ons (will it be able to?), that would probably solve most needs ... but there isn't even such an add-on.

The AutoText feature really does appear to be something of a killer app for the Blackberry.

Something you may not be aware of is that in Maemo 4/Diablo (and in Maemo 5?), there isn't really auto-correction. Instead (at least with the stylus keyboard), what happens is that, when you type two or more letters, you are offered a selection of several words below the keyboard which you can select with your stylus. So, for example, as soon as I type "fr" I'm offered "from" "free" "friend" and "friends" and I can select one of them. I see no reason that this helpful feature couldn't co-exist with the sort of autocorrection you are asking for.