Support for Ledes 2000/XML or whatever they are currently calling it.  It's about time  (yes, that's a pun, deal with it)

Alerts: The problem with the alerts is that the conditions are “and” instead of “or”.  An attorney can have 1 alert but what they need is the ability to set up multiple alerts for individual clients.

For example, if I want an alert when WIP hits $10k for client abc  and client def, timeslips checks the total of  the wip for those clients combined not individually.

Backups:  It would be nice to limit the number of backups being saved.  Scheduled backups can fill up a drive pretty quickly.

It would be great if PDF's could be attached to printed invoices.

Here's one, although it may be a personal preference.  When a version of the software has been released, and a few months later , a service release (or more than 1) has come out, why doesn't the product download include the service release?  2015 SR1 came out in August, but the product download does not have it built in.

Split billing for electronic bills.  Now, only the primary client exports slips (the adjustment exports for all files) and the fields are not always accurate.