so, I have a client now who is on a web host using Plesk on Windows, with php/mysql and such. I've only done LAMP development. Should most things work the same between the 2 environments? I'm hoping to move my clients CMS off of my server and onto their web host's. The CMS has certain features that I'm a little skeptical about how it'd work on a windows box, such as the functionality to upload, and thus write files to directories. anyone have any experience in the WAMP realm?

If you get an FTP or SSH server there, you can upload files with no difference. And the beauty of PHP and other scripting languages is in their portability. If you need something like multithreading and working with processes (fork etc), you may run into problems. But "normal" PHP+MySql is always portable.

I wouldn't expect the transition to go without a hitch. There are lots of little issues on windows that simply don't exist on a linux box....Having said that, however, your script will probably run (file uploads in PHP on windows do work, as long as the folder has the right permissions, just like in Linux)

I setup a php, mysql, apache site for a client that was moving from 1 host to another VPS. He's running the php nuke with some broadcasting software. Like the above post, there will be some bumps down the road which is why when making the transition you test the site out via IP before propagating the DNS over that way if indeed issue come up, #1 you're the only one (who know the new IP it'll be on) will be seeing it to prevent your client's clients from getting discouraged #2 have the ability and extra time needed to adjust/modify the script accordingly or perform research or workarounds to correct the issue.

it'll be trial and error and you will just have to thoroughly test it out before completing the move.

Not all scripts will work fine. If they are using linux specific commands, or, for example, work with linux shell - they will not work on windows.
Anyway, if you are working with standart functions - then no problems. I'm developing scripts on windows system, but develop them for linux

thanks everyone. I ended up making the move yesterday to test it out before changing where their site gets it data from. the only thing that seemed to cause issues was some _GET/_POST change-arounds. other than that, it seemed to work as planned. thanks for the help!