Yes I have. I have used each with the exception of only one!:
Espeon- Of course, my favorite of the bunch. I use her on my Sunny Day team. Great speed and great Special Attack. Not to mention her Magic Bounce just makes her one of the greatest Pokemon out there!
Umbreon- As a wall, this guy can easily annoy his opponent. The Toxic/Wish/Protect combination is just devastating. I used him on my Sunny Day team for a while, with Moonlight. He can work well with wonders on that weather team!
Leafeon- Last but not least, to my Sunny Day team before replacing it with Venusaur, I had Leafeon with her Chlorophyll. She can be a potential physical sweeper. She was really fun and exciting to use. Although most others seem to use her for Baton Pass, I like her style of battling :X
Jolteon- The guy's fast. Teach him Thunder and put him in a Rainy Day team, he can be a force to be reckon with. Although I never used him after 2nd Generation, just only in Pokemon Stadium and Gold/Silver/Crystal xD
Vaporeon- I used Vaporeon quite a bit here and there. Practically to be a staller and a Baton Passer to be quit honest. That's really all I ever used of Vaporeon xD
& Eevee- For Pokemon Online- I decided to make a Little Cup team and have Eevee on the team. Not sure when, but I'll let you know how it goes when I battle with it for the first time!
Flareon- I've used Flareon in Pokemon Stadium and I'm pretty sure I have used it in Generation 1, Red/Blue. I know I choose Vaporeon in Pokemon Yellow, so I couldn't had Flareon then. It's a shame they haven't put much work and speed into Flareon. Definitely a good one in my book, just not for battling!
Glaceon is the only one I have ever used. Maybe I should try out a Hail team and have him in?
I have used several of hs forms i hve a Lvl 100 Vaporeon, Jolteon, Flareon, Espeon and Umbreon :D
I have glaceon and leafeon but have never used them :/