Before there was Qt Creator, I suspect a lot of people were using Qt Designer with other tools that are intended for general use but don't offer explicit Qt support. This remains a valid approach, but be aware of the pros and cons.

One pro is that this is the most portable approach. Don't like the editor anymore.? No probs. Another is that this approach will force you to learn more of the Qt infrastructure at the beginning rather than when something breaks and your annoyance level is high.

On the con side, you won't get very complete code completion. Also, the lack of automation when adding forms, etc. means you will be doing a fair amount more manual coding. Both of these will slow you down and make you less excited about making changes.