I still have a 9780 unlocked that I use once in a while on Simple Mobile.
The thing about Berries, they were designed as a communication device first, and a smartphone second. If you are a fan of apps galore, you are never going to be happy with a Berry. It's not what they were designed to do.
Quite simply, they were designed to be a Personal Digital Assistant, designed around a phone. Like the old Palm Pilot phones were.
If you like a QWERTY keyboard, and fast email access, you can't beat a Berry. Nothing handles true raw communication power like they do. The legacy devices run on what is known as BIS (BlackBerry Internet Service) rather than other smartphones that run on the open internet. BIS is proprietary and very secure. And your emails are pushed to you, theoretically, as soon as BIS gets them. Because of this, you just can't pick up a legacy Blackberry and "start using it" on any old cellular system. You must get a true BlackBerry plan and register the device on the BIS network, OR, many things will not work, like email.
And advantage to BIS is, for contracted customers, you could use BIS internationally for pennies on the dollar VS typical smartphone roaming costs. That is, until T-Mo started free international data.
Like iPhone, the Berries were build to strict manufacturing details and quality "usually" was very good. Droid phones can be hit or miss as we all know.
The new Berries do not operate on BIS. They are more true "Smartphones" like Droids and iPhones. The company has also had a lot of issues. They may survive, but only time will tell.
The one issue I've got with any CDMA carrier like Virgin (Sprint) is that you can't just pop in a SIM card and go like you can with a GSM carrier.
Simple Mobile INCLUDES BIS with all their unlimited plans, so if you want to change between a Berry and a Droid and an iPhone, all you do is swap the SIM and you are set.
As I type this, I'm putting the SIM in my BlackBerry. I have a lot of emails to go through and I prefer doing this on the Berry.
