Yep, I chucked some of my ill-gotten gains into a First Save cash ISA a couple of years ago, and would bank with them again.
Once the bonus interest period expired after a year I opted to transfer the ISA to a provider paying a better rate. First Save were quite slow, to the point where I had to phone them up to find out how they were getting on with my transfer application. Three things impressed me - I got straight through to a real person when I phoned, their staff were polite and helpful and, without me asking, they readily offered to pay a compensatory amount in recognition of the delay.
So, ok they slipped up slightly, but these things happen and no company can get everything right all the time. I often think a good measure is how a company reacts when things don't go to plan and, in this respect, First Save delivered.
Plus, they are licenced by the Financial Services Authority (as FBN Bank (UK) Ltd), so savings up to £85,000 are covered by the Financial Services Compensation Scheme if they were to go bust.