I would also recommend an e-power. Ive tried one and it is a nice device.
Good suggestion! You will save a good deal of money in the long run with the E-Power over the Riva/eGo. Same size PV but the batteries cost $4-$5 instead of $20 and they last 5 times longer than the Riva/eGo batteries:
Electronic Cigarette - Starter Kits - E-Power
e-Power