PHP5.3 has been out for ages, but I’ve never used it because of web host support at this stage.
What version of PHP are you using for most of your sites, and what environment (shared, VPS, dedicated, cloud) are they hosted on?
Also, to those using PHP5.3 do you have cPanel installed on your server?
I use 5.3 and above, always the latest version. Currently I making a move to more cloud type services like Amazon EC2 and Windows Azure. However, been using VPS services out there for the most part.
logic earth — I gather you’re not using cPanel on your VPS either?
my web host provider gives us the option to use PHP4,5,6.
I choose to use the latest version of PHP5 until PHP6 becomes “official”.
Er, there is no PHP6; official or otherwise. 
from http://ostatic.com/blog/php-6-0-more-to-love-less-to-hate
PHP still has features and quirks that will continue to irk some programmers. But as PHP 6.0 comes closer to its final release, it seems safe to say that this new release will have more to love, and much less to hate
and if you set up an account with Awardspace you will get a select list in your control panel to choose either PHP4,5,6
see attached screenshot of my choices
Here’s a more authoritative source, note the lack of a PHP 6 branch. I’m pretty sure the next release will be 5.4; the features to be included in the 5.4 release are still being heavily debated, so ‘PHP 6’ appears to be quite a while off yet.
Of course, this is just my take on things. If you do find an authoritative source detailing the current state of ‘PHP 6’ though, I’d love to catch-up.
Anthony.
all I am saying is that I have the option to run PHP4,5,6 on my web host provider and that I am choosing to run PHP5 until PHP6 becomes “official”.
I am not saying the PHP6 on Awardspace is an official version yet.
When the screenshot I posted becomes visible, you will see a (dev) next to PHP6
I read yesterday that development on PHP 6 had been suspended temporarily (because of a few issues). I think the next version is going to be 5.4 instead of 6. That’s what I glean from this, anyway.
I use 5.3 across the board now. Generally, the latest stable version if it’s on my own servers or whatever is available elsewhere like 5.3.3 on the shared server with Site5. From all accounts, that seems to be a pretty unusual situation to be in but I’m certainly not complaining. (:
Not in production, I run the latest developer snapshots (of the 5.3 and trunk branches) as often as I remember to rebuild PHP. I’ve also got a server which currently runs 20-something versions simultaneously… but that’s another story entirely. :x
Because of the above, I tend to forget that most folks are still running 5.2 so very often suggest features which aren’t available to them yet. As for PHP 6, how about moving that to a new thread? There’s lots to be said but maybe not in this thread (hey, that rhymed).
5.2 on my shared hosting server. And I just realized it’s not the latest version. I ought to put in a ticket about that…
[edit]: aaand done 
Currently I am using 5.3.3. on a VPS with Cpanel.
I probably do not use very many up to date php functions etc. and most of my code would be OK on php 4.
I am using 5.3 in VPS server (for my personal blog) and having the option to use 4, 5.2 and 5.3.
5.2.14 on my live site (see sig), 5.3.3-1ubuntu9.1 on my dev machine.
Every now and then I use a 5.3 thingy which doesn’t work in the real world, but generally it’s not too troublesome that they’re not both the same version.
Using 5.3 on EC2. Used to use VPS (slicehost) but really impressed with how easy to use EC2 is.
Also, never been a big fan of cPanel
Thanks for the responses.
This article was posted today which sampled 12 million domains and gives me a good answer to my question (the version part anyway)
http://phpadvent.org/2010/usage-statistics-by-ilia-alshanetsky
I have 5.2.9 on VPS with Plesk, (with ServInt, I used SliceHost before too they are very good, I need a managed VPS though) … I could upgrade PHP but Im lazy 
I’m late coming back I know, been busy. X.X
Anyways, no I don’t use cPanel on my server. I keep the bare minimal running at all times and use SSH to have a remote terminal and do everything from there. Its pretty easy not having a GUI once you get used to and know what you are doing. Plus I find setting up PHP using FastCGI and secure accounts (Not using Apache’s or IIS default user account) for each website this way.
FastCGI is definitely the way to go, have you played with FPM (which is now in core since 5.3.3) yet?