Whilst the price is never as low as the headline grabbing figure, they are still WAY cheaper than any traditional carrier.
My OH & I have used them a fair bit to travel to her home country in the Baltics. The way you have to look at it is that it's a game. So you can get a a prepaid master card from Phones4U for £10. If there's two of you, it's just paid for itself. If there's more, you are saving!
Get/borrow the lightest cases you can and cram them. Wear your biggest items of clothing, including coat. Put as much stuff in your pockets as possible.
Take your own snacks (food can go airside) then get a bottle of water in the waiting area.
I've never bothered with priority boarding. It's not a big deal to me but if you have children, it's worth sending one adult in first to bag the seats for the rest of you.
As for old creaky planes, let me say I've never seen one. Ryanair have the newest fleet in Europe! The average age is 3 years which compared with BA is brilliant. They also have an enviable safety record and must comply to all EU safety rules. The way I see it is that O'Leary's too tight to pay for a new aircraft & the resulting compensation so he'd rather pay to have the maintenance done properly.
If you expect luxury then forget it. But if you think of it like a taxi and bear in mind what you are paying then it's good value.