I never really worked with Exabyte libraries myself so couldn't really say. What I would look at is the choice of tape drive you have inside the libraries - you may be surprised at migrating from a relatively cheap DLT solution to something like SDLT or LTO or AIT and not realise how expensive the actual media is in comparison to what you are using now.
Myself personally I prefer LTO. SDLT had a bit of a bad rep in it's early days for problematic firmware that made it appear as if it was very unreliable but it seems better these days. I rarely see any AIT at all in places I have worked so couldn't really comment on that either.
Another thing to bear in mind is not to set your sights on new tape drive/library hardware too high. For example you'd be really disappointed if you shelled out for a LTO3 drive and stuck it on a rickety old server which you can't afford to upgrade at the same time which couldn't keep up with it, and it actually gave less throughput than your existing solution.
To put it in simple terms tape drives have both an upper and lower throughput threshold. With newer drives it is less likely you will max out the throughput and more likely that you will come across issues of not being able to stream backup data fast enough from older servers to keep the minimum drive transfer threshold streamed. The consequence of this is that instead of writing a continous stream the drive has to stop, rewind a little and then start again once the data stream being backed up has caught up. This might mean that the throughput for your backup might be slower on your shiny new drive than it is on your old faithful one.
Good luck !
