I started on the Teva tablets - there's no problem with them, I just think you should be on a divided dose but that's your GP's call. I'd make an appointment and discuss it with him.
The standard tabs are fine but, as ven has a short half life, you'll get high blood levels for 12 hours after taking it and then the levels fall until your next tab. The options your GP should give you is standard tabs with divided dose or the modified release, once a day. I specifically asked mine about this years ago and he was clear not to take the standard ones once a day. It won't harm you, it just means you'll be a bit up and down and may feel a bit nauseous when you take them.
Putting all that aside as it's only really a minor point, stick with it and you'll really see the benefits.
Good luck
Pip