There are over 20,000 members at out church. I can't know the percentage that are baptised in the Spirit, but we promote it and teach it continually, and the invitation to receive is given in every service. I would venture that at least 80-90% are Spirit filled.
That said, when one receives this experience, it is still necessary to maintain the Spirit filled life. In other words, you have to stir up that gift, otherwise, you can go on to be as carnal as you were before.
I've seen many people, like myself be greatly affected by the infilling of the Spirit, and I developed a greater hunger for spiritual things. I've seen other people be gloriously filled, and then grow cold again.
When it comes to spiritual things, there is no getting by on yesterdays manna, and being Spirit filled will not cause you to achieve any status in God. We require many re-fillings after that initial baptism. A lot of Christians lack the discipline or desire to press in.
Being Spirit filled and speaking in tongues brings an awesome dynamic to the Christian walk. But these days, it seems many "pentecostal" people know little about it.