Admittedly Telnet clients are not the sexiest of apps out there, you won't hear the internet screaming for it like say Angry Birds. However if your BlackBerry PlayBook is used for business, there is good chance that you're in need of a decent Telnet SSH client. If you don't know what this product is most likely you will not need it. If you do, then you're always on the lookout for a different one with more options.
The Good:
Telnet SSH is a port of a very popular open sourced client called Putty for Windows. It does work and will let you establish a SSH connection to your server. It does a lot of things like negotiate encryption protocols and exchange authentication methods.
The software will allow you to define multiple sessions which is a great feature. The price point is excellent at only $1.99 and in a pinch is a very acceptable SSH client.
The Bad:
Although you can define multiple sessions, you can only connect to one at a time. It is also not possible to close one session and return to the connections screen, your must completely close the app an re-launch it.
One of the biggest problems is that the terminal does not redraw when you bring up the keyboard, meaning you can't see the lower half of your command line and need to type blindly. They keyboard remapping for the ESC key and CONTROL key are listed on the App World page but not obviously in the app itself.
As well, here is no internal menu for the program by swiping down from top of screen.
Summary:
Telnet clients seem to still be a work in progress but as I mentioned for in a pinch Telnet needs, for $2 you can't really go to wrong.