I copied this from the RIM site, see if this convinces you to get 4.5 Plus think about HTML email and Video recording on your Curve.
User Interface
* Refreshed Look – Enjoy messages, address book entries and a calendar that make better use of colors and fonts. They’re also laid out to more closely match the programs you use on your computer.
Email
* Improved Email Layout (Rich HTML Email) – View tables, images and fonts with formatting that looks better than ever.1
* Remote Search – Find emails that are stored on a BlackBerry® Enterprise Server.2,3
Attachments and Files
* Edit Microsoft® Word and Microsoft® PowerPoint® Files – Just download the attachments and start typing!
* Copy, paste, change font formatting and more.4
* Download and Save – Grab a file on the Internet, and save it to your smartphone to view or edit later.
Want to edit Microsoft® Excel® files on your BlackBerry smartphone? Visit the DataViz® website to register with DataViz and download an update for Documents To Go that includes Sheet To Go.
SureType
* Save Time as You Type – Word completion for SureType keyboards will monitor what you type and present a list of options to scroll through so you don’t have to type the whole word.
Browser
* Mobile Streaming – Access videos, music or even sports and news clips from websites with mobile streaming capabilities.5
BlackBerry® Maps
* Local Search - Enter a search term like ‘pizza’ to view a list of places to grab a slice within a 30-km radius.6
Voice Notes
* Send a Voice Note – Instead of typing an email, record a Voice Note and send it as an email attachment or Multimedia Message (MMS).
* Stay on Top of Your Tasks – Record your thoughts and play them back when they’re needed.
Music
* Improved Music Management – See all your music files, or filter them by artist, album or genre. You can even create and edit playlists.
* Musical Multitasking – Open the BlackBerry menu and select “Now Playing” to access the name and artist for the song you’re listening to – even when using another application.
* Bluetooth Compatible (A2DP) – Use wireless Bluetooth® headphones or speakers to enjoy your music wherever you are.7
Video
* Video Recording – Take it all in with video camera capabilities.3,8,9
* Full Screen Player – Watch videos in full-screen mode or stay in command with the media controls mode.
Calendar
* Free/Busy Lookup – View your colleagues’ calendars on your smartphone2,3
Check this link out to see if you can upgrade from RIM:
[Only registered and activated users can see links. Click Here To Register...]