Who recommended warfarin? Was it your GP or a cardiologist? If you haven't seen the latter, I would ask your GP to refer you for a second opinion.
If the AF is of recent onset, I would explore the reasons why you've developed the condition and see if it can't be rectified. If there's potential for it to be successful, cardioversion must be a better option than a life time of anticoagulation.
CJ, I can't see a causative link between warfarin use and a heart attack, but the condition that necessitated warfarinisation might have been the precipitant.
Certainly, there is a link between warfarin use and haemorrhagic stroke, often after fairly insignificant head trauma for obvious reasons. In the elderly, bridging veins between the brain and dura are under relative tension as the brain undergoes atrophy and literally shrinks away from the skull. These veins can be torn easily and lead to a chronic subdural haematoma; in the warfarinised patient, this may be a devastating acute bleed.
Warfarin is always a hassle, even if your levels are usually well controlled. Every new drug you're given can influence its metabolism make your blood too thin or not thin enough. That Christmas glass or two of wine that's more than your usual can have an effect, not to mention making accidents more likely with an associated risk of haemorrhage. If you need an operation, it may be delayed whilst your INR stabilises. Any trivial bleed - an ulcer, a haemorrhoid, a laceration - will be unnecessarily complicated by warfarin. The list of potential problems is endless...
The reason why you've been prescribed warfarin is to reduce your risk if embolic stroke. If your atria are beating irregularly and too rapidly, they will not empty of blood with each cardiac cycle. As such, there is a risk of stasis leading to thrombosis within the atria. If a piece of this clot from your left atrium detatches, it may travel in the vessels to your brain causing vascular occlusion and thence a stroke. There are many factors that govern your risk of forming such mural thromboses, just as there are many causes for atrial fibrillation - some reversible, some not. I strongly recommend you discuss this with a cardiologist who will be able to stratify your own particular risk and then advise you regarding your own need for warfarin and your potential suitablility for cardioversion. If their verdict is to use warfarin, then I'm afraid you're stuck with it! Good luck.