Within reason, no company or government is going to put forward an unsafe treatment/control issue when it comes to disease. I say within reason because a) novel drugs may have unexpected consequences that weren't looked for in screening and b) chemotherapy, for example, is rather unsafe, you have to admit.
As I understand it, the development of the swine flu vaccine is no different from the development of the normal yearly flu vaccine; it doesn't take years to develope or go through screening, as it is effectively what was done for many years, just with a different strain. Because of this, as I udnerstand it, it is no less safe than the standard flu vaccine.
Which is it's own kettle of fish. The flu vaccine won't protect you against this year's flu strain, but last year's. The flu virus is a fast mutating beast that alters its outer protein coat - the part that the immune system sees and recognises as something it has seen before, and something it must neutralise - very fast. This means that there is no way that it can offer 100% protection. However, it can offer you some protecting - your body will recognise the virus as a disease faster than it would without the vaccine.
The side effects will probably be the same as when you have a normal flu vaccine as well - that is to say, you might feel wretched for a day or two afterwards. Which isn't the virus somehow ressurecting and making you a vat of disease, but is your immune system going into overdrive. Most vaccines have something in them - called an adjuvant - which your immune system sees and freaks out about, causing a very strong immune reaction, so that the body is more likely to develope a memory response to the antigen. That's all immunity is - recognising and remembering something as foreign.
Of course, most flu symptoms are actually your immune response trying to clear an infection, which is why when people get achey and feverish following vaccination they assume that the vaccination made them sick. Strictly speaking, yes, but not in a lasting way - most flu vaccines are called "killed" vaccines, because the virus has been heat-killed and is incapable of reproducing and spreading. It's just little virus corpses with an adjuvant, and your immune system freaks out.
So, I'd say that the vaccine is going to be as safe as the normal flu vaccine - it might make you a bit under the weather for a while. It probably won't give you complete protection against swine flu. If you have an egg allergy, you might feel a bit sick and the doctors will want to stare at you for a while. But weigh that against the risk - what's feeling a bit crook for a while against the chance that you could get seriously, dangerously sick later?