I've walk into AP many times recently. But seldom get any attention of the sales person. They are normally busy serving foreigner customers. I prefer a place where the salesman have more patient serving me, i.e let me test the product before buying. I bought my first 2 SLRs from them, many year back, I had better service those days. I don't blame them for that, SIM LIM is a very crowded place especially in the weekends. It's better to go there weekdays
Basically, there are 2 kinds of shops, one like AP, where there are more customers than salesman and they sell you at the right price. This is where I like to go and get my stuff. I do not mind browsing around for the next available salesman - itls just a few minutes.
There are many other shops in Sim Lim where you see salesmen waiting for customers and no customer in their shop. They are catching flies. And if you enter, good luck to you.
So, it is up to you, which type of shop do you go to.
You can pay 550 for a $500 item in one of those "empty" or quiet shops, and you're served like a King, or rather fleeced like a furry sheep. Up to you.