I haven't been to your site but I can give you a laundry list of features that I look for. I use an internal network web application to track time with contractors and remote employees and we love it. At some point though we'll grow out of what we are using.

Multiple projects

multiple rates based on type of task and billing codes

client information tracking and ability for clients to track their time on a project or task and as though they were an employee just with special considerations

Provide the ability to "sell" blocks of time and track it on both the client and subscriber side as in service agreements or to track minimum time obligations.

Ability to distinguish when time goes from prepaid time to a new level based on thresholds

change billing rates to accommodate traditional employment rules and regulations (nights, weekends, over time, etc.)

Ability to "approve" times put in before any permanent record is made on select accounts or user profiles

Multiple locations and groups

Employee, Lead, Manager, and director levels of admin

Invoicing and statements

Ability to block out certain times where people CAN'T report work

Auditing so any changes, exceptions, or tampering is immediately logged and becomes legal evidence (database triggers are the best way)

Multiple level authentication, blocking IP's or IP ranges

time->revenue (t/r) tracking by project

t/r tracking by class of project

multiple increment break out based on class of task 10, 15, 20, 30, and 1 hour increments

Automatic time additions based on class of task ie: add 1 hour or half an hour of travel time automatically to field service calls

reporting by employee, project, class, department, division, etc.

export data to popular payroll software or provide interfaces to payroll software

Import data from PDA's, spreadsheets, and a system client

ability to update from web enabled phone or PDA

management "dash board" feature that gives reporting based on several time intervals and employee classes

History tracking and data backups to a client owned database/spreadsheet

Sick time and down time tracking (probably could be handled in work classes, but the reporting would be different)

Milestone tracking by sending notices to customers/managers when certain blocks of time are reached

Team time tracking

If you wanted to get really fancy you could provide some estimation tools based on past performance of a job or task class and matching some type of skill measurement to a task

Give me some time and I'll think of more.