I have had the HP Probook 4720s for about 7 months now, replacing a much older Toshiba Satellite Pro A100 which had performed admirably over a number of years (4+) heavy use.

As an IT consultant looking for a laptop for all purposes my requirements were very high. Put simply, I wanted the following:-

* Huge hard disk - the 4720s has 500GB (actually 450GB is available as the other 50GB is hidden for recovery)
* Lots of RAM as I want to be able to run virtual machines and capable of running SQL Server 2008 Developer/Enterprise (i.e. 4GB RAM minimum whereas old Tosh had 2GB max) - this comes with 4GB RAM, expandable to 8GB which I ordered at the same time
* future-proofed as much as possible as I probably won't be able to afford another one for another 5 years - this has Windows 7 Pro, facial recognition, fingerprint recognition, integrated webcam and microphone and almost every single connection that you can think of
* decent battery life - this was reputed to have 4 hours (the Tosh started with 2 and ended up with less than 60 seconds!)
* Sensible size for daily use but also portable - this has a 17" screen with separate numberpad, so no RSI for me! It is big to lug, but you get used to it.
* durable as the grey plastic on the Tosh was actually wearing out and massively discoloured - this one is a metal construction

Huge expectations then, and the HP Probook 4720s promised to meet most of what I needed for under £900. Today, 7 months later, I still have 290GB free on the hard drive, despite some seriously large downloads (how I managed with 70GB on the Tosh is unfathomable). I currently have MS Office 2010 Pro and SQL Server 2008 R2, along with other web development software and virtual machines. It still seems to be as future-proof as it was 6 months ago (a rare feat).

Where have I noticed problems?
* MS Outlook 2010 often stops working and closes. It then re-opens and cannot restart because a file is in use. The event logs indicate that the problem relates to the preloaded HP QuickLook Add-in integration with Outlook 2010. Simply waiting a few minutes and restarting Outlook is a temporary workaround.
* There are techniques to try to maintain a decent battery. I take out the cable when the battery has been fully charged and don't leave it plugged in overnight. I think it is starting to wear down, but slowly. The Tosh had halved its battery life in the first 6 months and I'm sure this still has over 3 hours grace.
* seems to be slower starting up now, so may need to think about making some adjustments
* a slightly disconcerting clicking sometimes eminating from the hard drive
* construction between the keboard and the DVD drive doesn't seem as sturdy as the rest

In summary, the HP Probook 4720s has and still is bearing up well to a hard life. It is a high spec machine, designed for heavy duty IT work in a solid construction. The only issue that really annoys is Outlook crashing so frequently. Hopefully HP will resolve this software bug soon.