Last Nov it took 5 min to clear immigration at DPS, there were over a dozen counters open (instead of the usual 2 or 3). So the authorities appear to be trying to help. Customs was very interested in number of bottles of duty free (luckily I had exactly the legal limit). The only priority line at DPS is for APEC, if you have that it comes in very handy (you skip VOA and can use the diplomatic line, which is usually empty). As stated the numerous escort services are somewhat scams, however they do bribe the staff and are usually able to use the crew line, which is sometimes faster. But I was quite impressed with my last trip to DPS how much faster and better it was than in the past. I guess the problem is there are many flights that land at certain times of day, and CX happens to have one of the worst arrival times from that standpoint.