I'm not going to spend any time getting into the details, how I arrived at these conclusions, etc. I'm sure plenty of you will disagree with this. That is okay.
The recipe for a fast Droid, simply put, is:
1. I am highly suspicious of themes. Stock is faster. I cannot prove this.
2. Non-stock "launchers" are very bad, at least right now. Don't use anything called "Launcher" or "Helix". Use the stock "Home" app. If you run CyanogenMod, you can install the stock Home from ROM Manager. Try it.
3. Overclocking appears to kick things up a notch. I'm on a 1.1ghz 5-slot, standard-voltage bebit kernel right now and all is well. I'm going to downgrade later today to the stock clockspeed for comparison.
4. App/task killers are bad. This has been discussed to death. Put some faith in Linux and Android.
I'll probably get buried for this, but yes, I'm essentially telling you that Motorola, Google, and Verizon pretty much got it right. Almost everything I've installed from the modding community has been a net performance hit compared to the stock system. At this point, the only reasons I remain rooted is for WiFi tethering and overclocking.
Sorry I gotta disagree for most of this, aside from a few spots.
Themes are Ok, they can slow down the phone, depends on how heavy they went on eye candy and if they correctly made the theme for the rom you're using. if you try flashing and old theme you saved on the brand new rom, yeah you'll have issues since you lose all the fixes in framework and whatnot.
Non stock launchers are by far faster, and more feature/option rich than the stock. the problem is people do not remove the data and completely uninstall the other launchers so they all clog up memory. They are much much faster than the stock launcher.
yes overclocking does add significant speed increase and coupled with setcpu can even save battery life in the process.
app/task killers can be bad or good. I suppose it depends on what you mean by it. It's nice to have something to kill apps that sometimes go haywire and will not close or get stuck as a zombie and android won't kill it (arggg go for the head!) but some things like autokiller which can help fine tune memory settings are a great addition and can speed things up a lot. just have to experiment with the settings. It can also kill apps/processes but it's not the main function. Though android usually does a good job and yeah just killing off apps isn't needed. but tweaking the kill off settings is great.
Want to really speed things up? get rid of all the crap.
-99% of you probably do not realistically need 7 home screens
-you do not want to plaster every home screen you do have with widgets,not only does it take up memory but a lot grab info off the network and thus use battery... aka more screens+widgets = more memory used and less battery life.
-Uninstall apps you don't use. If all you use is launcher pro or adw, uninstall completely the other launchers using adb or root explorer or whatever works. No need for it to be in the internal memory if it's not used.
-addition to the above, my list of usual instant removals on a new install are:
Old Launchers
facebook (don't use anyways and i hear market freebies are much better)
twitter (not sure, still hear market ones are better)
mp3 store(seriously? anyone use this thing? I haven't even run it, ever) Delete
geniewidget news weather thing. sucks always using memory and trying to access data. if you have beautiful widgets or weather widgets toggle, just delete this stupid thing, you'll be happy you did.
most people that don't use their phones for business or use exchange can probably remove email.apk and corp cal. (this is not the gmail email app)
vzw visual vm. maybe someone uses this? deleted =)
think that's most of them. Then set screens to 3 default to the middle one use a minimum of widgets... only one i use is beautiful for the clock / weather.
Doing all this I can hover around 100mb free idle. I know how linux memory works so it tries to cache things which is fine, but this gives me some headroom and keeps my phone snappy. Hell even helix2 could be flicked from one side to the other in one flick. so with these lightweight ones... whew fast!
**sorry didn't want to hijack the thread, but most people barely know how to install roms. I don't hear much about people properly uninstalling the crud they don't use, or I see screenshots of every screen packed with widgets ><
then they complain of being slow or having battery issues.
I reflashed cyanogen today to see if that would work. it ran perfectly til i themed it with hex fusion again. NOw i need a new theme