Is it just me, or does anyone else see a pattern here?

The biggest single reason I've seen on this forum for people having a crappy phone: They install crap without understanding what it is, what it does, or how it works. For the love of all things holy, if you don't understand what something is, or how it works, don't install it until you do! That includes "speed patches", applications, drivers, kernels, and even the beloved CSSU. If you can't read a wiki / thread for something and understand how it works, how to configure it, and what it's designed to do, you get what you deserve if you install it. Doubly so if it's from extras-devel or a random zip/deb file. Would you take a drug from a random person because they say it will make you feel better or run faster, with no indication of what it is, how it works, or if it's safe? Why would you do that to your N900?

I can tell you I've not missed a single call since PR 1.0, which had some problems with that without any mods at all. Since PR 1.1 it's been rock solid at answering calls. I can also tell you I have a crap-ton of stuff installed, including K49, h.e.n., CSSU, boat loads of apps, and with mild exceptions very few things have caused issues. (And most of those are things I hesitated installing, and didn't follow my own advice on. )

Some of the key things I advise people to do to "fix" problems like what you're having above (besides not installing crap) are as follows:

Orientation swap (portrait mode) - Solution: Just don't. Nothing was designed to run in portrait mode, not one blessed thing. It only works because of hacks and patches. Transitioning between the two can take forever, even with the cute "flip" animation turned off. I run CSSU locked in landscape mode, and it's just rock solid. This device was made and sold as a landscape device. If you wanted a portrait phone you made a poor purchasing decision, which the slide out keyboard should have clued you into pre-purchase.

Conversations Inbox Widget - Can occasionally cause the desktop to lock, crash, or run at 100%. It seems to always happen when an SMS is received, but causes the message to not show an indicator/beep. On killing hildon-desktop, or rebooting, the message comes through as it restarts, before widget show up. When I was running it, I found it's propensity to cause a lockup grew with the size of the database. (The same db file also houses e-mail, SMS, call logs, etc.) If you want to keep old messages, do so with glogarchive or via the OVI/PC suite. Since disabling this widget I've had 0 desktop freezes. Solution: Disable the widget, or at least clean up/remove old SMS & compact the database on occasion.

Swapspace fragmentation - Over time the N900 slows because the swap space becomes somewhat fragmented. This is a kernel issue and is common on pretty much all linux systems. It presents itself faster on the N900 because of the amount of swapping done in heavy usage. Solution: Every couple days turn off the main swap space, then turn it back on. If you have lots loaded (esp CSSU) you may need to setup a small swap space in a loopback device, or on the SD card and enable it for the excess to "spill" into when you turn swap off. That clears out all the old clutter and swaps back out only stuff it needs too. Or, just reboot on occasion.

And if you've already installed a crap-patch, without knowing what it's done, don't assume an uninstall will fix it. Lots of the patches change kernel values and tweak settings files when they run, which they don't undo when uninstalled. If you have a crappy system because you once installed crap, the simplest way to fix it is to do a backup, re-flash, and recover said backup. (Packages/contacts only!) The harder way is to figure out exactly what was done and undo it... but if you knew how to do that, you probably wouldn't have installed such a thing to start with.

And in case there's any doubt that an N900 can run stably for a long time, I submit this Conky screen shot, just taken a bit ago with my N900. Note the uptime.