Following link might assist, Sealine Beach is worthwhile if you want to escape the concrete
http://www.qatarairways.com/au/en/qatar-tours.page
If you enjoy a beer and TV sport then Champions Sports Bar at the Marriott City Center is recommended.
On a BA LHR-HAM flight a few years back the FA asked myself and another passenger if we wouldn't mind sitting in an exit row seat for take-off/landing. For some reason nobody had been allocated one and it was a requirement.
This is from 2011 and doubt anything changed as new airport still not operating: http://support.qatarairways.com/entries/20447606-Airport-left-luggage-facility-at-Doha-International-Airport