Update: This breaks root! If you're already rooted, download and flash the rooted version of the update. Thanks Steven.

If you had Swype beforehand and you install the update, you may have issues with it. If you do:

... go into the installed applications settings (not the swype settings). First you must clear the application data, then uninstall the application. Then you must shutdown the phone. Then, of course, you must turn it on again. Then you can tap & hold in any text entry field, and you’ll get an “Input method” selection dialogue where you can select Swype again.

Thanks Cortex Reaver.

Get excited, EVO owners: Sprint's in the process of pushing out an update for your device. We know, every update is exciting - but this one is especially so because it adds Swype as an alternate keyboard option. Aside from that substantial goodie, the changes include:

HTC Evo Maintenance Release - 3.70.651.1

-Blockbuster (including WM DRM 10)
-Kindle eReader
-Preloaded try/buy video game: NOVA from Gameloft
-Sprint Zone update
-Latest Telenav
-Latest Visual Voicemail Application
-Latest Sprint TV application
-SWYPE keyboard
-Scan Now Widget for 4G

Important Notes:
The new software version is: 3.70.651.1

The obvious downside is that the update packs a bit of spam (Blockbuster, Kindle, and NOVA). A shifty move on Sprint's part, but hey, it could be worse.

[Source: Sprint via Engadget, Phandroid]