I tried today to upgrade to 1.5.2, but it mainly failed due to a non-compatible multiverse plugin which runs all our inventories, portals and worlds.
For those who are new to the upgrade process, here is a recent email that I have sent out to someone who asked me to upgrade the server. I know this sounds like a rant, but I want people to understand that upgrading a client is nothing like upgrading a server.
I am aware that people like you who do not know how to downgrade then cannot play. And believe me, the last thing I want is to have an outdated server.
However it’s normally a several hour process. I have to wait for up to 25 plugin authors to update their software, download it, reconfigure several hundred lines of config files and then make several test runs to make sure everything works. However, if you go research plugins like Multiverse, which we need to run all portals, inventories and worlds, you will see that they did not release an official update since November last year. Not to mention the main server software, bukkit, which still failed to release a finished version since 1.4.7.
To make a long story short: I will upgrade as soon as I can. Right now, I cannot. People asking me to do so or even telling me that I should does not help.
You will have to learn how to downgrade, just like everyone else.
If you take even a fraction of the time it would take me to upgrade (which is not even possible right now), to learn how to use google and then to downgrade, you would be able play.