I got this phone through T-mobile's upgrade service.  The first unit they sent me seemed to have a lot of problems, so I sent it back and received another one.  The second unit had the exact same problems, which tells me that the phone is defective and it wasn't just a bum unit.  Again, these problems existed on TWO brand new pearl 8120s, so it wasn't a fluke:

Show-stopping problems:
- The battery cover is loose!  The cover does not sit snugly on the back of the phone, and it rattles around when you hold the phone to your ear.  People on the other end of the line complained about hearing a rattling noise.
- Wi-Fi interferes with your phone call.  I was very excited that this phone could connect to Wi-Fi, but it turned out to be a drag.  Any time the phone was downloading data (new Emails, messages, etc), if you were talking on the phone at the same time, the voice on the other end would sputter and lag until the data transfer was done.  This could last up to a minute or more each time.
- The operating system is unstable.  The very first day I had this phone, I was on a conference call for work and had the unit on speakerphone.  A couple of minutes into the call, the phone crashed and rebooted itself!  And this phone takes several minutes to boot up, so I missed a lot of my conference call.  The phone crashed/rebooted about once a day for the entire time I had it.

Other cons:
- Weak battery life.  With mixed web browsing and talking, the battery lasted just over a day.
- Web browsing.  Even when using my wireless internet and NOT EDGE, the browser would time-out or stall when loading web pages.  It often took me two or three attempts to load web pages.
- Poor choices for ring tones / wall papers / themes.
- Phone feels weak and flimsy to the touch.  If you drop it, you can kiss your new phone goodbye.
- The 2 MP camera took mediocre pictures even in direct sunlight.  Also, E-mailing those pictures (when taken at full resolution) essentially disables your phone until the Email upload is complete.  The phone becomes unresponsive and all you see is the hourglass waiting icon, for several minutes per picture.

Pros:
- Very light phone
- T-mobile didn't hassle me about returning both units when I was very unhappy with my new phone.
- Good voice quality (when not interfered by Wi-Fi or incoming messages)
- The SureType technology was nice for sending messages.

The cons FAR OUTWEIGH the pros.  I was extremely disappointed by this phone because I heard such great things about the previous version, the Pearl 8100.  The 8120 is flimsy, has manufacturing defects, and is very unreliable.  I'll never buy another blackberry again.
I got this phone through T-mobile's upgrade service. The first unit they sent me seemed to have a lot of problems, so I sent it back and received another one. The second unit had the exact same problems, which tells me that the phone is defective and it wasn't just a bum unit. Again, these problems existed on TWO brand new pearl 8120s, so it wasn't a fluke:

Show-stopping problems:
- The battery cover is loose! The cover does not sit snugly on the back of the phone, and it rattles around when you hold the phone to your ear. People on the other end of the line complained about hearing a rattling noise. - Wi-Fi interferes with your phone call. I was very excited that this phone could connect to Wi-Fi, but it turned out to be a drag. Any time the phone was downloading data (new Emails, messages, etc), if you were talking on the phone at the same time, the voice on the other end would sputter and lag until the data transfer was done. This could last up to a minute or more each time. - The operating system is unstable. The very first day I had this phone, I was on a conference call for work and had the unit on speakerphone. A couple of minutes into the call, the phone crashed and rebooted itself! And this phone takes several minutes to boot up, so I missed a lot of my conference call. The phone crashed/rebooted about once a day for the entire time I had it. Other cons:
- Weak battery life. With mixed web browsing and talking, the battery lasted just over a day. - Web browsing. Even when using my wireless internet and NOT EDGE, the browser would time-out or stall when loading web pages. It often took me two or three attempts to load web pages. - Poor choices for ring tones / wall papers / themes. - Phone feels weak and flimsy to the touch. If you drop it, you can kiss your new phone goodbye. - The 2 MP camera took mediocre pictures even in direct sunlight. Also, E-mailing those pictures (when taken at full resolution) essentially disables your phone until the Email upload is complete. The phone becomes unresponsive and all you see is the hourglass waiting icon, for several minutes per picture. Pros:
- Very light phone
- T-mobile didn't hassle me about returning both units when I was very unhappy with my new phone. - Good voice quality (when not interfered by Wi-Fi or incoming messages)
- The SureType technology was nice for sending messages. The cons FAR OUTWEIGH the pros. I was extremely disappointed by this phone because I heard such great things about the previous version, the Pearl 8100. The 8120 is flimsy, has manufacturing defects, and is very unreliable. I'll never buy another blackberry again.