Speedy boarding, and other forms of priority boarding on LCCs, are more of a curse for those who have it than a blessing, since in most cases now half the aircraft have it and all have to queue early or it's pointless. I often watch the queue from my seat in the gate area and chuckle indulgently as the queue forms 10 minutes before the incoming arrives, and the priority passengers stand stoically for 30-40 minutes awaiting the removal of the tensa barrier.
It's always interesting to compare airlines. I've flown 44 airlines so far this year, with 39 out of 163 flights on BA. My honest observation is that BA tends to offer the most pleasant SH experience in any cabin, the crews are uniformly ok to good, the cabins tend to feel comfortable. On J SH I've not felt that any other carrier is better.
When it comes to LCC, the entire proposition is different. You're not looking for comfort in particular, and anything that moves you towards a good experience makes you feel good. An aisle or window on a random selection, a free middle, somewhere close to the front or back, overhead space, all of these give you a bit of a boost. The law of expectations says that when you start low, it doesn't take much to exceed. That's a real problem for premium brands who start with faulty brand value perceptions from years or decades gone by,
I've never encountered a child in a middle CE seat or anyone else for that matter, and this would annoy me greatly. I would in that case have a word with the CSM but to be fair, the offer guarantees aisle or window seat, not a free middle, so I don't know how that conversation would go.