It can sometimes be annoying. The tab can sometimes be annoying also.
For example if I am doing an MRX and I want "MOTOR_1" in the "to domore address". Suppose I also have tags: MOTOR_1_RUN", "MOTOR_1_STOP", and etc. If I type in MOTOR_1 the drop down will cover the next field that I want to go to, which is "on success, set bit". If I hit tab it will pop off do a different field and I have to go look for it.
It's not really a problem, I'm just easily annoyed.