[AT&T, Rogers HTC One X, Telstra One XL] gridlock489:
By all means go for it! I have a few tips for you, as one flasher to another ;)

As redpoint said, each time you flash a new ROM you are starting from scratch. This only refers to your personal data and ROM settings, though. There are a few ways to guarantee that you won't be spending a long time configuring each ROM:

Cloud Storage is your friend! I personally use Dropbox to save anything important to my daily use since I can easily pull up documents stored there from anything connected to the internet. There are much more secure options to store files on the cloud, but you have to pay for the more secure options, and security is not of top importance to me (since I just store homework assignments and basic documents).

Use Google Backup! When you flash new android ROMs, there is a prompt that asks you if you would like to backup your phone to Google's servers. I usually hit yes to this prompt. After you have done this once, when you flash a new ROM and enter your Google account, any Play store apps you had installed will be redownloaded (including any personal data associated with the app, IF it's developer has enabled this feature). It's not a perfect way of restoring your apps, but it sure beats re-entering all of your data each time you want to try a new ROM.

Use services to store your contacts! I took a few days to enter ALL of my contacts into my Gmail account, and it was one of the best decisions I have ever made. Each time I restore my phone, I have all of my contacts available. People who complain about losing all of their contacts along with their phone need to learn about this point.

Remember that your SD card partition stays intact between ROMs! Just because you install a new OS doesn't mean you lose everything. Any music, movies, documents, or even app data that is stored on your SD card is unaffected by flashing something new. This is because your SD card is a completely separate partition of your phone's memory. The One XL may not have a real SD card slot, but you can still treat this partition as separate from the rest of your phone. Personal Tip: I store my backups and ROM zip files in a "Recovery" folder on my SD card partition. Having all of those files in one place simplifies flashing in TWRP.

Avoid using tools like Titanium Backup to restore apps! For a while I decided to use Titanium to restore apps. After a while I realized that all of the errors I was experiencing was the result of mismatched phone IDs, cache errors, and a bunch of other small glitches caused by Titanium backup. It is not the fault of TB and it is still a useful tool, but using Google backup to restore your apps is much cleaner and will result in fewer errors.

Save your text messages! Titanium Backup has the option of saving your text messages as a .xml file, but this is more complex than just using play store applications like SMS Backup & Restore. If you don't back up your SMS, you will look totally unpopular when you keep flashing your phone (and have no text messages at all)!

I hope this list helps you out in your flashing journey. Don't be afraid to try new things, and remember that if you can get into recovery mode, you will be fine (ESPECIALLY if you back up your data in the ways I described).