Here is my 2 cents. I upgraded my Curve 8330 to OS 5.0 from Boost yesterday. I did the delete vendor.xml and ran Loader.exe, as recommended in the CrackBerry article. I took a long time and ran fine. The 8330 does not have a lot of memory, and the 5.0 uses about 10 mB or more memory than the 4.5. Also, Blackberry Maps does not work (I've heard that it is because Boost does not have it on their BBs), which is no big deal for me since I use VZNavigator. Memory became the big issue for me, even after deleting some unused apps. This morning I had the bright idea to reinstall OS 5.0 using BlackBerry Master Control Program (http://mcpfx.com) which allows you to NOT install some core items like default themes, VAD, BBIM, and some other programs. In all I saved 15 mB in not loading those core apps I don't need and brought my free memory up to an acceptable limit. Remember to back up your phone using the Desktop Manager & Master Control Program (third party apps). You must leave the Dimension ZEN theme installed for any themes to work, but get rid of the rest. As for 5.0, the default browser is extremely fast, I was able to get rid of Bolt & Opera Mini browser. It also has memory compression which allows you to operate with less free memory (I think). I really like 5.0 so far. It is a big improvement over 4.5 both in features and speed.
The Boost 5.0 is a very new build and is much faster than 4.5 on the old guy. I agree that removal of any of the unwanted items is a must and I always like to keep 12mb free on all of my berries.
Additional comments on memory, now that I've been using it for a few days. The handy applications QuickPull & RestartMe don't work with 5.0. I did a search and found that if you press the Alt, right shift & Del keys simultaneously, it does the same thing, a simulated battery pull. This was very handy for me since I have an Otter Box case which is hard to get into to do a battery pull. When I tried it my free memory went from 15 mb to 25 mb.
I saw a posting over on Crackberry where sombody was told by a VZW tech that the "official" os 5 was probably not going to be relased for the 8330 because they're in the process of phasing them out. Which sucks...I've only had mine for 5 months.
I personally don't think there will be a 5.0 for the 8330. Even if you install it before loading any apps, you will not have enough memory left to put any number of apps on there. It would just make those 8330 owners frustrated when they try to load apps and realize they don't have too much memory left to do so. As far as retiring the 8330, I think it might be in the picture. It was a workhorse. According to an article today on Crackberry, it is supposed to be one of the best selling smartphones. I'm sure the price had a lot to do with that.
Actually, on my 8330, the 188.8.131.52 release seemed to fix a lot of my gremlins (as did formatting the SD card with the phone), and I'm actually fairly happy with it. The main reason I wanted 5.0, and really the only thing I'm actually CRAVING, is that sweet, beautiful clock. If anybody knows how I could get that, on it's own, I'd be a happy man.
I am running VZ Nav. I find you need to make sure you don't let your free memory drop too much or VZ Nav will not find the GPS. I just do a soft reboot (Alt+Right Shift+Del) before I take my trip.
I was getting tired of the memory leak associated with the Boost OS 5.0. I was ready to go back to 4.5. Then I installed a hybrid OS from www.nathanix.com last week. If you follow the instructions (it is no harder than installing the Boost OS 5.0) you can delete many of the apps that you don't use (default ringtones (see post about freeing memory), themes, foreign language support, etc). It is very stable and I have had no more memory leak issues. In fact, the OS recovers memory after you close open applications. I very rarely have to perform a soft reboot. I highly recommend it.