Question for the gunnies

Do any of my readers use a shot timer to practice with on a regular occasion, either live training at the range or dry fire at home? Both? If you do has the timed training significantly improved your abilities, specifically pertaining to self defense shooting and concealed carry? Has the use of a timer made a noticeable improvement in your presentation speed and effectiveness down range? For years I have been "concealed carry" practicing (live fire) by simply making a concerted effort to shoot as fast as possible while keeping all my bullets on target. Of course it's not very scientific and while I might "feel" I'm shooting fast I really don't have anything to compare it to, it's all subjective on my part. I'm thinking it's time to move my training up another level. If you have personal experience with this your opinion would be helpful.