While my architect wasn't perfect, he were very happy overall with what he did for us.
The design he came up with was a complete departure from the lines along which the previous architect we'd been using (and fired) had been going. It was far better, and more importantly, it was something we had a chance of getting planning for.
Unlike many (indeed most) architects, ours is an absolute whizz at the planning process. He's very familiar with local and national planning policies, and shepherded our extremely modern design through to first time approval in a very conservative area. I like to think we helped by actively engaging with the community and our neighbours first (because we wanted to, I should add, not just because we wanted to get planning permission!), but the planning submission was a work of art.
He didn't have many serious weaknesses. If there's one thing I think he could do with some work on it's his weathering details. Some of them really didn't manage water very well, but thankfully these were picked up and rectified by others before it was too late.
There are two things I'd counsel:
1. You MUST get a fantastic personal feeling from the architect at every point until you sign up. Any misgivings, or misunderstandings, or odd vibes are a warning - if that happens now, it'll be HELL when things inevitably get stressful.
2. There are exceptions to the rule, but choose an architect whose buildings you like. There are very few architects who are so talented that they can design (or indeed are interested in designing) many different types of building well. Ours is a specialist in modern designs, and we largely liked what he'd done before. Don't go along to a specialist in neo-Georgian and expect them to design you a modernist temple!