Absolutely YES!!! After mastering a move slowly, you'll be amazed how soon you'll be able to do it faster than you ever imagined. While you are practicing slowly today, in a few weeks/months you'll be way beyond where you would be if you primarily practice at higher speeds.
Musicians and athletes use this technique all the time to master extremely complicated material. Martial artists are famous for practicing their crafts in slow motion, ("wax on, wax off"), because that is the way the masters work it even after they can break bricks (or heads) as needed. The very slow repetition builds mind-body connections that allow extremely accurate motions at high speeds when desired.
When dancing faster many people are sloppy but the speed covers for them, making it tough to see the exact movements. Practicing slow takes all the momentum out of the moves and gives you different insights. It provides the mental bandwidth to focus on the details. It also trains the mind-body connection in ways that are different from practicing a move quickly. This can be more difficult than practicing faster, and it often exposes weaknesses that are not obvious when moves are flying by at breakneck speed.
When practicing slow you either need to count out loud, play slower than normal music, or find a fast song and practice everything with a "half-time" feel, where you take 2 counts to do everything you would normally do in a single count. All moves take twice as long and it can be a very interesting experience. I actually use half-time concepts on the dance floor with high speed music. It can have a very dramatic effect when used at the right time. (I'll detail half-time in another article.)
An excellent tune for slow practice is "Biggest Part of Me" by David Pack. This is an old 1980's hit that has been remade with a salsa feel, (same vocalist who did the original). For my hard core readers; It is NOT a true salsa tune, but an excellent practice tune, with a great salsa feel. I downloaded it from iTunes and for a buck it's worth having in your practice tunes list. I can't remember hearing a tune this slow in a salsa club but I love it for practicing. (This is one of the tunes I use when teaching.)
After working a move or combination painfully slow, then getting comfortable at normal tempo, be sure to switch gears and try it at extreme speeds. In other words, practice very slow, your regular tempo, and then extra fast. The feel of moves change with the tempos and mastering a wide range of tempos make your dancing much more solid. Plus when you are dancing at normal tempo, you have what seems like "extra time" because your mind is comfortable at the faster speed.
That said, practicing fast when you can't do it slow is a recipe for sloppy dancing. I do practice fast and highly recommend it, but that is only after mastering a move at a slow and medium tempo.
I built myself a song-list that has the tunes arranged from mind-numbing slow to blisteringly fast. When practicing I can select tunes from this list and quickly transition between the different tempos. You can put this type of playlist together on your iPod or burn yourself a CD with your favorites arranged by tempo.
Take all your favorite moves and try them very slowly, then regular speed and then wickedly fast. Practicing slower is a master's secret that few use to its maximum advantage. Each tempo is related but uses different thinking processes and using a wide range will make all your motions dramatically better. If you do this regularly, you'll be amazed how much progress you'll make.
Ambition by itself never gets anywhere until it forms a partnership with hard work.